MAT  6     UW9 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

i 
Class 


NATURE    TEACHING 


NATURE  TEACHING 

BASED      UPON      THE     GENERAL 
PRINCIPLES     OF     AGRICULTURE 

FOR    THE    USE    OF    SCHOOLS 


BY  FRANCIS  WATTS,  B.Sc.,  F.I.C.,  F.C.S. 

GOVERNMENT   ANALYTICAL  AND  AGRICULTURAL   CHEMIST,   LEEWARD  ISLANDS, 
WEST  INDIES 

AND  WILLIAM  G.  FKEEMAN,  B.Sc.,  A.E.C.S.,  F.L.S. 

SUPERINTENDENT  OF  THE  COLONIAL  COLLECTIONS,  IMPERIAL  INSTITUTE  J   LATE  SCIENTIFIC 

ASSISTANT,   IMPERIAL  DEPARTMENT   OF  AGRICULTURE   FOR  THE   WEST  INDIES, 

AND   FORMERLY   DEMONSTRATOR   IN   BOTANY,   ROYAL  COLLEGE  OF 

SCIENCE,   LONDON 


NEW  YORK: 
E.    P.    BUTTON    £    CO. 

1904 


L  D 


GENERAL 


Printed  in  Great  Britain 


PREFACE 

THIS  little  book  was  originally  written  for  use  in  the 
West  Indies,  with  the  intention  of  shaping  the  courses 
of  study  both  in  secondary  and  primary  schools  ;  being 
employed  as  a  text-book  in  the  former,  while  in  primary 
schools  it  is  used  by  the  teachers  in  preparing  and 
formulating  their  teaching. 

As  it  has  been  found  useful  in  its  original  form  in 
the  West  Indies,  it  has  been  suggested  that  an  edition, 
rewritten  and  modified  to  meet  the  circumstances  of 
British  conditions,  may  prove  acceptable  in  the  mother 
country.  I  have,  therefore,  with  the  assistance  of  Mr  W. 
G.  Freeman,  prepared  the  present  revised  edition. 

Elementary  nature  teaching  admits  a  wide  range  of 
subjects,  and  individuality  plays  an  important  part ;  but 
throughout,  if  good  work  is  to  be  done,  it  must  be 
impressed  upon  the  teacher  that  the  pupils  must  do 
things  for  themselves.  Mere  knowledge  of  how  things 
ought  to  be  done,  and  what  they  ought  to  look  like  if  only 
they  were  found  and  seen,  is  of  little  value,  and  the 
absence  of  the  true  practical  knowledge  of  things  is 

a  2 

180730 


vi  PREFACE 

soon  revealed  upon  any  attempt  to  ascertain  the  depth 
and  reality  of  the  pupil's  information. 

For  this  reason  but  few  illustrations  are  used,  lest 
both  teacher  and  pupil,  seeing  how  things  appear  in  an 
illustration,  may  consider  that  "they  know  all  about 
that,"  and  may  be  tempted  to  shirk  the  effort  of  seeing 
the  natural  object  for  themselves. 

In  schools  where  the  subject  is  taken  up  for  the  first 
time,  it  will  probably  be  found  prudent  to  do  a  consider- 
able amount  of  work  before  attempting  anything  like  a 
formal  school  garden.  To  this  end  a  great  deal  of  useful 
work  can  be  done  by  growing  plants  in  pots  or  boxes. 
Ideas  for  the  school  garden  will  soon  evolve  themselves 
from  this  work. 

It  must  be  clearly  understood  that  the  book  is  not 
arranged  in  such  a  manner  as  to  afford  a  course  of 
instruction  to  be  taken  in  the  precise  order  in  which 
it  is  written.  In  work  of  this  kind  some  skill  and 
judgment  are  required  to  adjust  matters,  so  that 
the  teaching  shall  be  so  distributed  as  to  proceed  in 
an  even  manner  from  week  to  week,  and  also  that 
there  shall  be  no  unnecessary  delays,  as  may  arise 
from  waiting  for  some  experiment  or  demonstration 
to  mature. 

In  the  appendix,  attempts  are  made  to  indicate  suit- 
able courses  of  work  according  to  the  time  of  year  at 
which  the  work  is  begun,  but  in  this  there  is  ample 
scope  for  the  exercise  of  judgment  on  the  part  of 
the  teacher.  Nor  are  the  exercises  put  forward  as 
final;  they  are  only  indicative  of  a  general  course 
of  study,  and  the  intention  is  that  the  teacher  shall 


PREFACE  vii 

extend  and  modify  them  as  surrounding  conditions 
demand. 

In  some  instances  a  school  garden  cannot  be 
provided,  but  in  rural  districts  this  may  usually  be 
obtained.  It  is  not  necessary  to  have  a  large  piece  of 
ground. 

In  connection  with  school  gardening,  difficulty  is 
sometimes  experienced  in  maintaining  order,  and  pre- 
venting what  should  be  serious,  though  interesting, 
teaching  degenerating  into  a  useless  scramble.  This 
may  often  be  obviated  by  introducing  the  elements  of 
a  simple  drill  into  the  out-door  work,  as  by  marching 
the  class  to  the  tool-house,  then  passing  out  the  tools 
to  the  class  as  it  stands  in  rank,  and  marching  to  the 
plots  where  work  is  to  be  done,  and  so  on. 

In  the  working-plots  themselves  the  work  must  be 
carried  on  in  a  manner  similar  to  that  of  a  laboratory ; 
each  pupil  must  have  an  idea  of  what  he  is  aiming  at, 
and  proceed  independently  to  the  fulfilment  of  his 
object.  In  many  cases  it  is  well  for  the  pupils  to  work 
in  pairs. 

In  the  garden  itself,  two  kinds  of  work  have  to  be 
distinguished,  and  it  is  well  to  keep  them  distinct  in  the 
minds  of  teacher  and  pupil.  Some  plants  are  to  be 
grown  with  the  object  of  studying  their  mode  of  growth : 
they  are  to  be  examined,  and  possibly  destroyed  in 
process  of  examination,  in  various  stages.  Other  plants 
are  to  be  grown  for  the  sake  of  the  crop  they  afford, 
whether  the  crop  be  ornamental,  as  in  the  case  of  flowers 
and  decorative  plants,  or  useful,  as  in  the  case  of  fruits 
and  vegetables.  The  proper  arrangement  of  both  kinds  of 


viii  PREFACE 

work  requires  care  and   thought   on   the   part  of  the 
teacher. 

In  all  the  work,  drawing,  measuring,  and  weighing 
should  be  insisted  on  wherever  circumstances  permit 

F.  W. 

August^  1903. 


Official  duties  having  called  me  to  Southern  Nigeria 
for  some  months,  it  has  been  impossible  for  me  to  revise 
the  final  proofs. 

My  deepest  thanks  are  due  to  my  wife  for  kindly 
undertaking  this  laborious  task,  and  compiling  the 
index,  in  addition  to  the  valuable  assistance  she  has 
given  throughout  the  progress  of  the  work ;  and  in 
particular,  in  preparing,  especially  for  this  book,  the 
whole  of  the  illustrations.  W.  G.  F. 

February  28,  1904. 


CONTENTS 

CHAPTER  I 

THE  SEED 

The  Parts  of  a  Seed — Plant  Food  in  Seeds — Germination — 
Practical  Work— The  Conditions  of  Germination— Rais- 
ing Seedlings  —  Seed  Beds  —  Observations  on  Seed- 
lings— Testing  Vitality  of  Seeds  .... 


CHAPTER  II 

THE  ROOT 

Uses  of  Roots.  Practical  Work — Root-Hairs — Root-Caps — 
Growth  in  Thickness — Growth  in  Length — Absorption 
by  Roots — Roots  and  Gravitation — Roots  and  Water — 
Propagation  by  Cuttings  .....  24 


CHAPTER  III 

THE  STEM 

Uses  of  Stems— Structure  of  Stems— Grafting  and  Budding. 
Practical  Work — Uses  of  Stems— Structure  of  Stems 
— Grafting  and  Budding  .  .  .  .  .41 


x  CONTENTS 

CHAPTER  IV 

THE   LEAF 

PACK 

Uses  of  Leaves  —  Structure  of  Leaves  —  Transpiration — 
The  Atmosphere — Plants  and  the  Atmosphere — The 
Food  of  Plants.  Practical  Work— Uses  of  Leaves- 
Structure  of  Leaves — Transpiration — Plants  and  the 
Atmosphere — The  Food  of  Plants  .  .  .66 


CHAPTER  V 

THE  SOIL 

Water  in  Soils— Clay— Vegetable  Matter  in  Soils— Chalk 
in  Soils.  Practical  Work — Mechanical  Analysis  of  Soil 
— Water  in  Soils — Vegetable  Matter  in  Soils — Chalk  in 
Soils  101 


CHAPTER  VI 

PLANT   FOOD  AND   MANURES 

Nitrogenous  Matter — Leguminous  Plants  and  Nitrogen — 
Mineral  Matter — Manuring — General  Manures — Nitro- 
genous    Manures  —  Phosphatic     Manures  —  Potassic 
Manures.     Practical   Work  — The    Food    of  Plants- 
Experiments  with  Manures — Leguminous  Plants  .       122 


CHAPTER  VII 

FLOWERS  AND  FRUITS 

Parts  of  a  Flower — Uses  of  the  Parts  of  a  Flower—  Insects 
and  Flowers — Wind-Pollinated  Flowers — Fruits  and 
Seeds — Dispersal  of  Fruits  and  Seeds — Variation  in 


CONTENTS  xi 

PAOE 

Seedlings.  Practical  Work— Parts  of  a  Flower— Ex- 
periments in  Cross-Fertilisation — Dispersal  of  Seeds — 
Wind-Borne  Seeds — Dispersal  by  Water — Dispersal  by 
Animals — Dispersal  by  Explosive  Action  .  139 


CHAPTER  VIII 

WEEDS 

Practical  Work — Preserving  Plant  Specimens  .  164 

CHAPTER  IX 

ANIMAL  PESTS  OF  PLANTS 

Life-History  of  a   Caterpillar — Life-History  of  a  Beetle — 

Remedies.     Practical  Work — Remedies  .  .  .169 

GLOSSARY         .......      179 

APPENDICES— 

I.  Suggested  Courses  .  .  .  .185 

II.  Apparatus  and  Materials  Required    .  .  .186 

INDEX   ........      189 


NATURE    TEACHING 


CHAPTER    I 

THE   SEED 

(S 

IN  all  agricultural  and  gardening  work,  seeds  are  so 
constantly  employed  for  the  purpose  of  raising  new 
crops  that  every  one  is  more  or  less  familiar  with 
them. 

We  know,  as  the  result  of  experience,  that  if  we  sow 
seeds  we  shall  in  the  course  of  time  obtain  young  plants 
or  seedlings,  and  that  these,  if  properly  looked  after, 
will  grow  into  large  plants,  and  in  due  course  flower  and 
bear  seeds  themselves,  from  which  a  second  crop  of 
plants  can  be  raised.  This  order  of  events  is  the  same 
whether  our  experience  has  been  gained  by  growing 
poppies,  mignonette,  hollyhocks,  etc.,  in  the  garden,  or 
wheat,  turnips,  and  clover  in  the  field,  or  whether  we 
have  been  practically  engaged  in  starting  a  new  oak 
wood  from  acorns. 

We  have  learnt  also,  as  the  result  of  our  experience, 
that  each  seed  has  apparently  hidden  away  in  it  the 
beginnings  of  a  new  plant  of  the  same  kind  as  that  from 

A 


2  NATURE  TEACHING 

which  the  seed  was  obtained,  and  that  if  we  wish  to  grow 
bean  plants  we  must  sow  bean  seeds,  and  acorns  if  we 
wish  to  raise  oaks. 

We  know,  also,  that  although  a  dry  seed  is  to  all 
appearances  a  mere  dead  thing,  it  soon  springs  into  life, 
or  germinates,  if  we  place  it  in  a  warm  place  and  give  it 
a  supply  of  moisture. 

Moreover,  we  are  aware  that  even  dry  seeds  cannot 
be  stored  for  a  very  long  time  without  gradually  dying, 
for  the  farmer  or  gardener  who  is  anxious  to  raise  good, 
full  crops  is  careful  to  secure  good  seed,  obtained  usually 
from  the  crop  of  the  season  before,  and  does  not  sow 
any  old  seed  which  may  be  to  hand. 

This  general  knowledge  is  most  valuable,  inasmuch 
as  it  is  the  outcome  of  the  practical  or  experimental 
work  of  ourselves,  and  of  those  before  us  who  have 
handed  down  their  results.  It  is  not,  however,  enough 
in  itself,  and  we  should  endeavour  to  understand  how, 
and  as  far  as  possible  why,  the  events  follow  each  other 
with  such  certainty. 

A  correct  knowledge  of  the  seed  and  of  the  conditions 
for  its  germination,  and  for  the  successful  growth  of  the 
seedling  and  plant,  touches  the  very  foundation  of  that 
sound  agricultural  practice  so  essential  to  success  at  the 
present  time. 

The  Parts  of  a  Seed. 

In  order  to  distinguish  the  various  parts  of  a  seed, 
it  is  best  to  examine  one  which  has  begun  to  grow,  or, 
as  is  more  commonly  said,  to  germinate,  for  in  this 
condition  the  parts  can  be  more  easily  separated  and 


THE  SEED  3 

distinguished.  Among  the  simplest  and  most  easily 
understood  seeds  are  any  of  the  ordinary  peas  or  beans. 
An  examination  of  a  very  young  plant  of  the  French  or 
kidney  bean — one  which  has  just  made  its  appearance 
above  the  surface  of  the  soil — will  reveal  the  following 
parts :  two  thick  leaves  (in  the  case  of  the  scarlet  runner 
and  some  others,  these  leaves  do  not  come  above  the 
surface  of  the  soil);  between  these  there  is  a  very  small 
leaf-bud  with  minute  leaves,  whilst  below  there  is  a 
stem  which  terminates  in  a  root,  the  root  itself  being 
branched. 

The  parts  of  the  young  bean  plant  should  now  be 
compared  with  a  bean  seed  which  has  not  germinated, 
but  which  has  been  soaked  for  a  few  hours  in  water  in 
order  to  soften  it.  The  seed-coat  will  strip  off  without 
difficulty,  and  it  will  then  be  found  that  enclosed  by 
the  seed-coat  is  a  structure  which  easily  splits  into  two 
halves,  and  a  little  thought  will  show  that  these  two 
halves  correspond  to  the  two  thick  leaves  which  have 
been  spoken  of  already.  These  leaves  are  called  the 
cotyledons  or  seed-leaves.  Between  the  cotyledons  there 
will  be  seen  a  small  curved  body,  one  portion  of  which, 
when  the  seed  germinates,  becomes  the  stem  with  leaves 
upon  it,  while  the  remaining  portion  develops  into  the 
root.  These  portions  are  known  respectively  as  plumule 
and  radicle.  With  the  help  of  a  pocket  lens,  the 
plumule  is  seen  to  consist  of  very  small  leaves  folded 
together.  There  thus  exists  in  the  seed  a  minute 
plant  with  rudimentary  root,  stem,  and  leaves.  When 
seeds  are  placed  under  suitable  conditions  these  rudi- 
mentary organs  grow,  and  the  seed  is  said  to  germinate. 


4  NATURE  TEACHING 

Plant  Food  in  Seeds. 

The  first  stages  of  germination  take  place  at  the 
expense  of  the  store  of  plant  food  which  exists  in  every 
seed.  In  the  case  of  the  bean,  which  has  just  been 
examined,  the  store  of  plant  food  is  contained  in  the 
thickened  seed-leaves.  If  some  germinating  kidney 
beans,  growing  in  soil,  are  observed  from  day  to  day, 
it  will  be  seen  that  the  seed-leaves  gradually  become 
smaller  and  smaller,  and  finally  shrivel  up.  In  the 
scarlet  runner  a  similar  thing  happens,  although  here 
the  cotyledons  never  came  above  the  surface  of  the 
ground.  A  great  many  plants  with  which  we  are 
familiar  have  their  supply  of  plant  food  for  germination 
stored  away  in  the  seed-leaves  ;  this,  for  instance,  is  the 
case  with  all  the  peas  and  beans,  with  the  seeds  of 
oak,  apricot,  cabbage,  radish,  lettuce,  cucumber,  orange, 
and  many  others. 

There  are  many  seeds  in  which  the  store  of  plant 
food  for  germination  is  not  contained  in  the  seed-leaves, 
nor  in  any  other  part  of  the  small  plant  in  the  seed,  but 
exists  as  a  separate  store.  In  these  seeds  we  find 
inside  the  seed-coat  an  embryo,  as  in  the  bean,  but  only 
small  cotyledons,  and,  in  addition,  a  separate  store  of 
plant  food.  These  may  be  made  out  in  the  seed  of 
buckwheat,,  marvel  of  Peru,  etc.,  where  the  embryo  is  to 
be  seen  enveloping,  but  perfectly  distinct  from,  the  store 
of  plant  food  which  makes  up  the  greater  portion  of 
the  seed. . 

In  wheat,  barley,  maize,  etc.,  the  embryo  lies  at  one 
side  of  the  seed,  near  the  pointed  end  (base),  and  easily 


THE  SEED  5 

distinguishable  as  a  white  patch.  In  maize  or  barley 
which  has  been  soaked  for  a  few  hours  in  water,  the 
embryo  may  be  readily  separated  from  the  rest  of  the 
seed,  when  it  will  be  seen  how  large  a  part  of  the  seed 
is  occupied  by  the  store  of  plant  food. 

This  separate  store  of  plant  food  is  often  spoken  of 
as  the  albumen*  and  seeds  are  described  as  albuminous 
or  exalbuminous  in  accordance  with  the  presence  or 
absence  of  this  albumeru  The  seeds  of  wheat,  barley, 
maize,  all  the  cereals  and  grasses,  beet,  carrot,  buck- 
wheat, marvel  of  Peru,  onion,  and  date,  afford  examples 
of  albuminous  seeds. 

If  we  now  refer  again  to  the  seed-leaves  or  cotyledons 
which  exist  in  every  seed,  we  have  to  note  that  the 
embryos  of  some  seeds  have  two  cotyledons,  as  in  the 
case  of  the  bean  and  buckwheat,  while  the  embryos  of 
other  seeds  have  only  one.  Barley,  wheat,  or  maize  may 
be  taken  as  examples  of  the  latter  class.  In  some 
cases  it  is  an  easy  matter  to  ascertain  whether  one  or 
two  cotyledons  are  present  in  the  seed,  while  in  others 
it  is  matter  of  some  difficulty.  It  is  found  that  the 
presence  of  either  one  cotyledon,  or  of  two  cotyledons, 
is  usually  associated  with  other  constant  characters  of 
plant  structure  to  which  fuller  reference  is  made  later. 
Seeds  with  embryos  having  one  cotyledon  are  described 
as  monocotyledonous,  while  those  in  which  two  cotyledons 
are  present  are  known  as  dicotyledonous. 

*  The  term  "albumen"  is  an  unfortunate  one,  as  the  same 
term  is  commonly  employed  to  denote  a  large  class  of  chemical 
substances.  There  should  be  no  difficulty,  however,  in  under- 
standing the  limited  sense  in  which  it  is  employed  here. 


6  NATURE  TEACHING 

Germination. 

When  a  gardener  or  farmer  sows  seeds,  he  takes 
care  to  proceed  in  such  a  manner  in  preparing  the  soil 
and  placing  the  seeds  in  it  as  previous  experience  has 
shown  him  produces  the  best  results.  It  is  well,  then, 
that  we  should  learn  what  takes  place  during  germina- 
tion, in  order  that  we  may  know  what  conditions  are 
essential  to  success. 

If  on  alternate  days  a  few  seeds  of  various  kinds  of 
beans  are  planted  in  moist  soil,  and  this  is  continued 
until  those  first  planted  have  developed  into  small 
plants  some  four  or  five  inches  high,  an  ample  supply 
of  material  may  be  to  hand  for  purposes  of  study. 

Take  a  bean,  which  has  been  soaked  in  water  but 
not  planted,  remove  the  seed-coat,  separate  the  cotyle- 
dons, and  bring  into  view  the  body  lying  between  them. 
Next,  dig  up  carefully  one  or  two  of  each  of  the  beans  of 
different  ages  and  compare  them  with  the  ungerminated 
seed.  There  will  be  no  difficulty  in  recognising  that 
germination  produces  changes  whereby  that  portion  of 
the  embryo  known  as  the  radicle  develops  into  the  root, 
whilst  the  plumule  becomes  the  stem  with  its  leaves.  The 
cotyledons  become  smaller  and  smaller  as  the  develop- 
ment of  the  young  plant  proceeds,  the  stores  of  food 
which  they  contain  being  used  by  this  young  plant  to 
build  up  its  own  structures. 

This  is  one  of  the  simplest  methods  of  germination ; 
but  we  should  observe  that  the  young  and  tender  plant 
has  certain  definite  objects  to  attain.  The  plantlet 
must  get  out  of  the  seed-coat,  and  it  must  be  able  to 


THE  SEED  7 

force  its  way  through  the  soil  in  which  the  seed  is 
sown. 

Observation  of  germinating  kidney  beans  shows  that 
the  root,  on  its  emergence  from  the  seed,  does  not  grow 
straight  down  into  the  soil,  but  bends  in  an  arch  near  the 
seed  and  then  grows  straight  downwards.  This  arch  is 
generally  the  first  thing  which  makes  its  appearance 
above  the  soil,  and,  from  its  form  and  structure,  is  well 
fitted  to  thrust  aside  the  particles  of  earth.  After  the 
arch  is  formed,  the  young  plant  is  firmly  anchored  in  the 
soil  by  means  of  the  root. 

The  arch  has  now  another  duty  to  perform  ;  the 
seed-coat  still  covers  the  cotyledons  and  the  plumule  ; 
these  must  be  liberated.  The  seed-coat  is  held  fast  by 
the  soil  sticking  to  it ;  the  arch  continues  to  grow  in  an 
upward  direction,  and,  as  a  result,  the  cotyledons  are 
withdrawn  from  the  seed-coat,  much  in  the  same  manner 
as  a  hand  is  drawn  out  of  a  glove.  When  this  is  done, 
the  arch  straightens  out  and  the  plant  grows  into  an 
upright  position. 

In  order  that  the  seed-Coat  may  be  held  firmly  by  the 
soil  and  not  be  drawn  out  by  the  plant's  movements 
during  germination,  seeds  are  frequently  provided  with 
projections,  spines  or  hairs,  which,  becoming  attached  to 
the  soil,  afford  the  necessary  firmness  of  hold.  In  some 
cases,  for  instance,  linseed  (flax)  and  cress,  the  seeds  are 
provided  with  a  seed-coat  which  becomes  mucilaginous 
and  sticky  when  wet,  thus  effecting  the  same  purpose. 

On  looking  over  a  plot  where  a  number  of  beans  are 
germinating,  it  may  often  be  noted  that  some  of  the 
seeds  have  not  been  able  to  rid  themselves  of  their  seed- 


8  NATURE  TEACHING 

coats,  owing  to  the  fact  that  the  soil  did  not  hold  down 
the  coats  sufficiently  firmly,  so  that  they  were  pulled  up 
when  the  plant  tried  to  draw  out  the  cotyledons.  Such 
plants  are  often  greatly  hindered  in  their  growth  by  the 
presence  of  these  no-longer-wanted  coats.  Cases  such 
as  this  should  be  borne  in  mind  in  attempting  to  dis- 
cover what  are  the  uses  of  spiny  or  warty  coats  of  many 
seeds. 

In  some  seeds,  for  example,  scarlet  runners,  peas,  and 
acorns,  the  seed-leaves  are  not  drawn  out  of  the  seed- 
coats  in  the  manner  described,  but  remain  below  the 
ground.  The  young  stem  makes  its  appearance  above 
ground  in  an  arched  form,  but,  in  this  case,  the  arch  is 
formed  above  the  point  of  attachment  of  the  cotyledons 
to  the  plumule.  The  growth  of  the  arch  now  merely 
draws  out  the  plumule  with  its  tender  leaves.  The 
young  plant  lives  for  some  time  on  the  store  of  food 
in  the  cotyledons,  which  gradually  become  thin  and 
shrivelled,  exactly  as  in  the  case  of  the  French  bean, 
where,  coming  above  ground,  the  changes  in  the  cotyle- 
dons are  more  easily  watched. 

The  seeds  of  the  vegetable  marrow  and  cucumber 
exhibit  interesting  peculiarities  in  their  germination. 
The  root  makes  its  appearance  first,  and  assumes  the 
curved  or  arched  form  in  a  similar  manner  to  that  of  the 
bean.  The  seed  being  flat,  usually  lies  upon  one  side. 
On  the  other  side  of  the  arch,  and  quite  close  to  the 
small  hole  through  which  the  root  makes  its  appearance, 
there  is  formed  a  protuberance.  This  protuberance 
catches  the  lower  edge  of  the  seed-coat  and  holds  it 
firmly  against  the  soil.  The  cotyledons,  still  within  the 


THE  SEED  9 

seed-coat,  are  soon  thrust  upwards  by  the  curved  form 
of  the  growing  root ;  this  leads  to  the  splitting  of  the 
seed-coat  into  two  halves,  whereby  the  young  plant  is 
set  free.  It  is  worth  observing  that  the  protuberance  is 
only  formed  on  one  side,  the  under  one ;  and  that  if, 
when  germination  has  proceeded  to  a  slight  extent,  the 
seed  be  turned  over  so  as  to  bring  the  upper  side  to  the 
under  side,  then  a  protuberance  will  form  on  the  side 
finally  downwards.  This  will  happen  even  if  a  slight 
protuberance  has  begun  to  form  before  the  turning  took 
place. 

In  the  instances  of  germination  already  referred  to, 
the  supply  of  plant  food  is  stored  in  the  cotyledons, 
whence  it  readily  passes  to  the  growing  parts  of  the 
young  plant.  In  those  cases,  however,  where  there  is  a 
separate  store  of  plant  food,  that  is  in  albuminous  seeds 
there  must  exist  some  means  whereby  this  food  can  be 
made  use  of  by  the  young  plant.  It  will  be  well  to 
describe  one  or  two  examples  showing  how  this  is 
accomplished. 

The  common  buckwheat  affords  an  interesting  and 
readily  observed  case.  If  some  buckwheat  is  sown  in  a 
pot  of  sawdust,  seedlings  can  easily  be  obtained  in 
various  stages  of  development  for  us  to  see  that  as  in 
the  preceding  cases  the  radicle  first  bursts  through  and 
grows  downwards  into  the  soil.  Above  ground  appears 
the  little  stem,  not  as  a  mere  arch  as  in  the  bean,  but 
curled  round  in  a  complete  loop,  bearing  at  the  free  end 
the  whole  seed,  with  the  cotyledons  still  inside.  The 
cotyledons  remain  enclosed  for  some  time  in  the  seed, 
which  fits  them  as  a  kind  of  cap.  Slowly  they  throw  off 


10  NATURE  TEACHING 

the  husk,  and  open  out  as  a  pair  of  green  leaves.  The 
husk  will  then  be  found  to  be  quite  empty,  all  the  food 
it  contained  having  been  absorbed  by  the  cotyledons  and 
passed  on  to  the  young  plant.  Whilst  this  is  going  on 
the  stem  has  also  straightened  out. 

The  onion  has  an  albuminous  seed.  In  germination 
the  young  root  first  makes  its  appearance,  and,  immedi- 
ately afterwards,  there  appears  the  lower  portion  of  the 
cotyledon.  This  assumes  the  arched  form  as  described 
in  the  case  of  other  seeds;  the  tip  of  the  cotyledon 
however  is  not  withdrawn,  but  remains  for  some  time 
within  the  seed-coat  in  contact  with  the  supply  of  food 
stored  up  there.  Upon  the  portion  of  the  cotyledon  in 
contact  with  this  food  there  is  formed  what  may  be 
described  as  a  sucker,  an  absorbing  organ,  which  takes 
up  the  stored  food  arid  passes  it  on  to  the  growing 
plant.  When  all  the  food  store  has  been  absorbed,  the 
cotyledon  is  withdrawn  from  the  seed-coat  and  the 
young  seedling  becomes  erect,  the  cotyledon  being  now 
green,  and  acting  as  an  ordinary  leaf. 

A  somewhat  similar  condition  of  things  occurs  in 
the  germination  of  the  seeds  of  many  palms,  and  may 
be  studied  in 'the  date.  The  germination  of  the  seeds 
of  the  date  palm  is  of  great  interest,  inasmuch  as  it 
supplies  an  excellent  illustration  of  the  way  in  which 
many  plants  overcome  the  difficulties  of  their  surround- 
ings. The  date  palm  is  well  known  as  a  plant  which 
can  thrive  in  sandy,  desert  regions,  where  the  water 
supply  is  scanty.  Most  ordinary  seedlings  are  delicate, 
and  easily  killed  if  kept  without  water.  How  then 
does  the  young  date  palm  manage  to  survive?  As  the 


THE  SEED  11 

seed  germinates,  it  puts  out  a  structure  which  bores 
down  into  the  soil  like  a  root.  As  we  shall  see  later, 
this  is  much  more  than  a  root,  and  really  consists  of  the 
root,  cotyledon,  leaf-bud,  and,  in  fact,  the  whole  of  the 
young  plant.  The  upper  portion  remains  inside  the 
seed  and  gradually  absorbs  all  the  food  contained  in  the 
seed,  passing  it  down  to  the  young  plant,  which  gradually 
is  thrust  quite  deep  down  in  the  soil.  Here  it  forms  its 
roots,  so  that  when,  later  on,  the  first  green  leaves 
appear  above  the  surface,  the  little  seedling  date  palm 
has  well-grown  roots,  and  can  get  water  for  itself  from  the 
deeper  layers  of  the  soil,  and  is  thoroughly  able  to  exist 
even  through  very  dry  weather,  when  many  seedlings 
would  die.  In  this  manner  the  seedling  date  grows  at 
the  expense  of  the  hard  food-supply  stored  up  in  the 
seed  as  the  hard,  horny  substance  which  makes  up  a 
date  "stone." 

The  seeds  of  the  castor-oil  plant  are  albuminous ; 
when  germination  takes  place  the  albumen  is  withdrawn 
from  the  seed-coat,  together  with  the  cotyledons,  the 
albumen  remaining  attached  to  the  back  of  the  cotyle- 
dons. The  plant  food  is  then  absorbed  during  the  first 
few  days  after  germination. 

The  seeds  of  all  the  ordinary  grasses  and  cereals  are 
albuminous.  The  manner  in  which  the  store  of  plant 
food  is  absorbed  during  germination  can  be  studied  in 
the  case  of  barley  and  maize.  Some  grains  of  each 
should  be  planted  on  three  or  four  successive  days,  in 
moist  sand  or  sawdust,  so  as  to  furnish  a  number  of 
specimens  in  different  stages  of  germination.  Thdse 
should  then  be  compared  with  grains  in  an  ungerminated 


12  NATURE  TEACHING 

condition,  and  with  some  which  have  merely  been  soaked 
for  a  few  hours  in  water  to  soften  them. 

On  examining  the  grains,  the  embryo  or  "  germ  " 
may  be  seen  as  a  white  patch  lying  on  one  side  of  the 
grain  near  the  pointed  end  ;  in  the  case  of  those  grains 
which  have  been  soaked,  the  embryo  can  be  readily 
detached  from  the  rest  of  the  seed.  The  seed  is  mono- 
cotyledonous,  and  careful  examination  of  the  detached 
embryo  shows  that  the  single  cotyledon  does  not  grow 
or  extend  through  the  seed-coat,  but  forms  the  means  of 
communication  through  which  the  reserve  of  plant  food 
passes  into  the  young  growing  plant.  The  cotyledon, 
here  known  as  the  scutellum^  lies  upon  the  surface  of  the 
albumen,  which  in  these  seeds  consists  almost  entirely 
of  starch.  As  soon  as  germination  begins,  the  scutellum 
secretes  a  digestive  fluid  which  converts  the  insoluble 
starch  into  soluble  substances,  which  are  readily  absorbed 
by  the  scutellum  and"  passed  on  to  the  growing  plantlet, 
lying  on,  and  attached  to,  the  other  side  of  the  scutellum. 
As  the  starch  is  dissolved  and  used  up,  the  scutellum 
presses  forward  into  the  vacant  space,  finally  taking  up 
all  the  starch  and  leaving  the  seed-coat  empty.  While 
this  is  going  on,  the  young  plant  is  growing  in  size, 
thrusting  its  roots  into  the  soil  and  its  leaves  into  the 
air,  so  that  by  the  time  the  supply  of  starch  within  the 
seed  is  exhausted  it  is  able  to  obtain  its  own  food. 

PRACTICAL  WORK 

The  following  exercises  are  suggested  in  illustration 
of  the  principles  already  discussed ;  they  may  be  per- 
formed by  the  pupils  themselves  or  by  the  teacher,  and 


THE  SEED  13 

used  by  him  as  demonstrations  in  his  object-lessons. 
They  admit  of  considerable  modification  and  variation, 
and,  in  their  present  form,  are  merely  intended  to  be 
suggestive.  The  precise  manner  in  which  they  are  con- 
ducted must  necessarily  depend  on  the  circumstances 
surrounding  each  class  of  students,  but  too  much  stress 
cannot  be  laid  on  the  advantage  of  the  pupils  actually 
performing  all  the  experiments  for  themselves  whenever 
there  are  no  reasons  rendering  this  quite  impossible. 

The  Conditions  of  Germination. 

Moisture,  air,  and  warmth  are  necessary  for  the  ger- 
mination and  continued  growth  of  seeds.  In  order  to 
demonstrate  this,  take  four  rather  small  but  wide-mouthed 
bottles,  two  of  which  are  furnished  with  good  corks. 
Label  these  bottles  A,  B,  C,  and  D  respectively.  In  A, 
having  first  taken  care  that  it  is  perfectly  dry,  place 
some  dry  seeds  (wheat,  barley,  peas,  or  beans),  cork  the 
bottle,  and  seal  with  sealing-wax  or  beeswax.  In  B, 
place  two  or  three  layers  of  wet  blotting-paper  at  the 
bottom,  then  put  in  the  seeds,  and  cork  and  seal  as 
before.  Treat  C  exactly  as  B,  but  leave  the  bottle  un- 
corked. 

Place  seeds  in  bottle  D,  and  then  fill  the  bottle  com- 
pletely with  water,  which  has  been  boiled  and  allowed  to 
cool,  to  drive  out  the  air  it  contains.  By  this  means  the 
air  originally  in  the  bottle  is  displaced  with  water,  and 
now  closing  the  bottle  with  a  cork,  we  have  the  seeds 
wet  but  with  practically  no  air. 

Put  A,  B,  C,  and  D  away  side  by  side,  preferably  in 
a  dark  place,  and  examine  daily.  It  should  be  found  that 


14  NATURE  TEACHING 

in  A  the  seeds  do  not  germinate  at  all ;  they  have  no 
water  at  all,  and  very  little  air.  In  B  the  seeds  have 
water  but  again  very  little  air;  they  will  probably  ger- 
minate and  grow  for  a  short  time,  and  then,  having 
exhausted  the  air,  die.  The  seeds  in  C  have  water,  and, 
the  bottle  being  open,  air  also.  (The  blotting-paper  in 
C  should  be  kept  moist  by  the  addition  of  water  from 
time  to  time.)  They  should  germinate  and  grow  well. 
Those  in  D,  although  provided  with  water,  have  no  air. 
They  should  grow  but  slightly,  if  at  all.  The  experi- 
ment has  so  far  shown  the  necessity  of  water  and  air. 
Keep  careful  notes  of  this  experiment,  recording  the 
number  of  seeds  which  germinate  at  all  in  each  bottle 
and  the  heights  the  seedlings  attain. 

In  order  to  show  the  influence  of  temperature,  take 
two  pots  filled  with  soil,  properly  prepared  for  the  recep- 
tion of  seeds  (see  p.  1 5).  In  each  pot  place  two  or  three 
seeds  of  several  different  kinds,  for  example,  beans,  peas, 
barley,  radish,  etc.  Label  the  pots,  and  place  one  out  of 
doors  and  keep  the  other  indoors  in  a  warm  place,  such 
as  in  the  kitchen,  or  warm  school-room.  Keep  the  soil 
in  both  pots  suitably  moist.  Note  in  your  note-book  the 
date  when  the  seeds  were  sown  and  the  dates  on  which 
the  various  seedlings  first  appear  above  the  surface  of 
the  soil.  Measure  the  heights  of  the  young  plants  at 
regular  intervals.  Compare  the  rate  of  germination  and 
early  growth  of  the  plants  in  the  pot  kept  warm  and  in 
that  exposed  to  cold,  and  draw  conclusions  as  to  the 
effect  of  temperature  upon  plant  life. 

Note. — This  experiment  should  be  made  between 
the  months  of  October  and  March. 


OF 

NIVERSITY] 

J    THE  SEED  15 

Raising  Seedlings. 

Observations  are  readily  made  on  seeds  sown  in 
boxes.  For  this  purpose  it  is  necessary  to  provide  suit- 
able boxes  and  material.  The  boxes  should  be  shallow, 
from  4  to  6  inches  in  depth,  with  sides  securely  fastened 
so  that  they  may  bear  the  weight  of  the  moist  soil.  A 
number  of  holes,  about  half  an  inch  in  diameter,  should 
be  bored  in  the  bottom  of  each  box  in  order  to  secure 
free  drainage.  In  addition  to  wooden  boxes,  useful  seed 
boxes  may  be  made  from  large  biscuit-tins. 

The  soil  for  filling  the  boxes  should  be  prepared  by 
Sifting,  first,  through  a  sieve  having  holes  of  about  an 
inch  in  diameter ;  this  removes  the  large  stones :  the 
sifted  soil  should  next  be  passed  through  a  second  sieve 
having  holes  of  about  a  quarter  of  an  inch  in  diameter ; 
this  separates  the  gravel  from  the  fine  soil.  A  small 
quantity  of  soil  should  be  passed  through  a  still  finer 
sieve.  It  is  advisable  to  prepare  a  good  supply  of  soil 
and  to  store  it  in  a  dry  place,  so  that,  whenever  required, 
stones,  gravel,  or  fine  soil  may  be  available. 

A  tool  is  useful  for  levelling  and  lightly  pressing  down 
the  soil  as  it  is  placed  in  the  boxes.  This  is  simply 
supplied  by  a  piece  of  smooth  board,  half  an  inch  in 
thickness  and  about  8  by  4  inches  in  area,  with  a  suit- 
able knob  or  handle  fixed  on  the  back. 

A  supply  of  dry,  finely-chopped  grass  (for  instance, 
lawn  mowings)  or  preferably  coco-nut  fibre  refuse,  is 
also  required. 

To  prepare  a  box  for  sowing  seeds,  place  at  the 
bottom  a  layer  about  I  to  2  inches  deep  of  the 


16  NATURE  TEACHING 

stones  separated  from  the  soil  by  means  of  the  coarsest 
sieve.  Over  the  stones  place  a  layer  of  about  the  same 
depth,  of  coco-nut  fibre  or  of  the  dry  chopped  grass,  to 
prevent  the  finer  material  choking  up  the  spaces  between 
the  stones.  Over  the  fibre  or  grass  put  a  layer  of  the 
gravel,  and  fill  up  the  box  with  sifted  earth.  Level  this 
last  layer  by  means  of  the  tool,  at  the  same  time  com- 
pressing the  earth  slightly.  If  the  soil  is  very  dry  it  is 
advisable  to  water  it  now,  as  less  damage  is  likely  to  be 
done  than  by  heavy  watering  after  the  seeds  have  been 
sown. 

The  seeds  may  now  be  sown,  the  method  of  proced- 
ure depending  on  the  size  and  kind  of  seed.  If  small 
seeds,  like  lettuce,  are  being  sown,  all  that  is  necessary 
is  to  scatter  them  evenly  and  thinly  over  the  surface,  and 
then  to  distribute  a  layer  of  the  very  fine  soil  over  the 
seeds,  sifting  the  soil  lightly  on  and  adding  only  so 
much  as  is  required  to  cover  the  seeds  without  burying 
them  at  all  deeply.  If  larger  seeds,  such  as  peas  or 
beans,  are  being  sown,  place  them  in  shallow  furrows, 
lightly  marked  out  with  a  piece  of  stick  or  with  the 
finger,  and  cover  with  very  fine  earth  as  in  the  previous 
case.  Very  large  seeds,  such  as  horse  chestnuts  or 
acorns,  may  be  placed  in  position,  buried  by  pressure 
about  half  their  own  depth  in  the  soil,  and  then  covered 
with  moderately  fine  earth. 

Everything  being  completed,  press  the  soil  gently 
down  with  the  tool.  This  pressing  down  has  the  effect 
of  producing  a  firm  seed  bed  which  is  necessary,  in  certain 
instances,  to  enable  the  young  plants  to  free  themselves 
from  their  seed-coats.  It  also  serves  to  keep  the  top 


THE  SEED  17 

layers  of  soil  moist,  for,  if  left  loose  and  dusty,  they 
would  become  dry,  and  the  seeds  would  suffer  from  lack 
of  moisture. 

After  the  seeds  have  been  sown  the  box  must  be 
watered.  This  requires  care,  or  delicate  seeds  will  be 
washed  out  of  the  ground.  A  watering-can  having  a 
rose  with  very  fine  holes,  should  be  used,  and  the  water 
only  allowed  to  fall  very  gently. 

The  boxes  should  be  placed  in  a  shady  place  where 
they  are  screened  from  heavy  rain  and  excessive  sun- 
shine. It  is  often  of  advantage  to  cover  the  box  with  a 
sheet  of  glass.  In  this  way  the  air  is  kept  moist,  and 
germination  usually  hastened.  The  glass  also  prevents 
damage  by  rain  if  the  boxes  cannot  be  placed  under  a 
roof. 

In  order  to  observe  the  effect  of  a  firm  seed  bed  sow 
onion  seeds  in  two  boxes  or  pots.  Compress  the  soil  of 
one  firmly  after  sowing  the  seeds.  In  the  other  cover 
the  seeds  lightly  with  sifted  soil,  avoiding  carefully  any 
compression.  Tend  the  boxes  or  pots  carefully,  and 
note  the  difference  in  the  manner  the  two  sets  of 
seeds  germinate  and  the  seedling  grow,  recording  your 
observations  in  your  note-book  and  making  drawings 
and  diagrams  of  the  seedlings  as  they  grow.  Similar 
experiments  may  be  made  with  seeds  other  than  onion. 
These  experiments  should  also  be  tried  in  garden  beds 
which  are  left  to  receive  no  watering  beyond  the  natural 

rainfall. 

Seed  Beds. 

Seeds  are  generally  sown  in  garden  beds,  or,  young 
seedlings  raised  in  boxes,  are  transplanted  to  beds.  The 


18  NATURE  TEACHING 

preparation  of  a  seed  bed  requires  some  care.  Select  a 
spot,  sheltered  as  much  as  possible  from  the  sun  and 
wind,  and  near  the  water  supply ;  remove  all  the  weeds 
and  fork  the  ground  to  a  good  depth.  Mark  out,  by 
means  of  a  line  (see  below),  the  paths  which  shall 
separate  the  beds ;  these  paths  should  be  about  2  feet 
wide,  while  the  beds  themselves  should  be  from  3  to  5 
feet  wide.  Having  marked  out  the  position  of  the  paths, 
and  while  the  line  is  still  stretched  in  place,  remove 
with  a  spade  the  soil  from  the  paths  and  distribute  it 
evenly  over  the  beds.  If  this  is  properly  done  the  paths 
should  now  be  about  6  or  8  inches  below  the  level  of 
the  beds.  Remove  all  stones  with  a  rake,  and  so  make 
up  the  beds  that  the  centre  of  each  is  slightly  higher 
than  the  sides.  This  is  of  great  importance,  as  it  allows 
water  to  drain  off  freely,  for  nothing  is  more  detrimental 
to  good  gardening  than  to  have  water  lying  in  pools  on 
the  beds. 

When  working  on  a  garden  bed  avoid  walking  upon 
it  When  weeding  or  planting,  it  is  often  necessary  to 
place  the  foot  upon  a  bed  in  order  to  reach  a 
particular  spot ;  in  this  case  use  a  foot-board,  which  is 
simply  a  narrow  piece  of  board  which  can  be  laid  across 
the  bed,  and  upon  this  only  should  any  one  be  permitted 
to  place  his  foot  when  working.  Another  appliance  in 
frequent  use  is  a  line  for  marking.  A  line  consists  of  a 
length  of  moderately  stout  cord  having  a  pointed  stake 
about  1 8  inches  long  attached  to  each  end.  It  is  well 
to  have  two  lines — a  long  one  for  laying  out  beds, 
paths,  etc.,  and  a  short  one  for  working  across  beds. 
After  use,  lines  should  always  be  neatly  wrapped 


THE  SEED  19 

around  their  stakes,  and  carefully  put  away  in  the 
tool-house. 

When  seeds  are  to  be  planted  in  a  garden  bed 
proceed  as  follows  : — Stretch  a  line  across  the  bed,  and, 
with  the  hand,  open  a  furrow  in  the  soil  along  the  line, 
making  the  furrow  of  a  depth  suitable  to  the  kind  of 
seed  to  be  sown,  2  inches  deep  for  large  seeds,  an  inch 
or  less  for  small  ones.  Having  made  one  furrow,  move 
the  line  the  required  distance,  fix  it  in  position,  mark 
out  another  furrow,  and  so  on.  In  regulating  the 
distance  between  the  rows  it  is  convenient  to  have  a 
piece  of  stick  of  the  same  length  as  the  distance  the 
rows  are  to  be  apart,  and  to  use  this  as  a  measure  to 
mark  the  new  position  of  the  line  every  time  it  requires 
to  be  moved ;  this  secures  regularity  and  neatness  of 
work.  The  furrows  being  opened,  scatter  the  seeds  by 
the  hand  along  the  bottom  of  each,  care  being  taken  to 
scatter  them  evenly  and  not  too  thickly.  When  the 
seeds  are  in  position,  gently  draw  the  soil  over  them, 
and  after  they  are  covered  apply  a  little  pressure  to 
render  the  soil  around  them  firm. 

Pots  are  sometimes  used  for  sowing  seeds  in,  par- 
ticularly large  seeds.  They  are  also  of  use  when  the 
young  plants  are  to  be  transferred  subsequently  to 
another  spot,  as,  for  instance,  cucumbers.  Pots  are  pre- 
pared for  seed  sowing  in  the  same  manner  as  boxes. 
In  the  tropics,  pots  made  of  bamboo  are  frequently 
used,  and  are  indeed  invaluable.  They  are  made  from 
large  bamboos  by  cutting  them  across  with  a  saw  just 
below  each  node  or  joint ;  the  division  or  partition  found 
at  each  joint  thus  forms  the  bottom  of  the  pot,  and  when 


20  NATURE  TEACHING 

a  hole  has  been  made  in  this  to  permit  of  drainage  the 
pot  is  ready  for  use. 

Observations  on  Seedlings. 

The  pupils  should  sow  all,  or  at  any  rate  the  greater 
number,  of  the  seeds  in  the  list  below,  the  teacher 
deciding  according  to  circumstances  whether  they  are 
to  be  sown  in  boxes,  pots,  or  beds.  All  the  various  stages 
in  their  germination  must  be  watched,  and  the  observa- 
tions recorded  in  suitable  note-books,  drawings,  even  if 
only  roughly  diagrammatic,  being  insisted  on.  As 
germination  proceeds  a  few  of  the  seeds  should  be 
removed  at  intervals  for  purposes  of  study  and  observa- 
tion. At  this  stage  of  the  pupils'  work  the  object  is  not 
to  raise  crops,  but  to  understand  how  crops  grow.  The 
observations  recorded  should  determine  the  method  of 
emergence  of  the  young  plant,  the  curves  assumed  by 
the  young  root  and  stem,  the  manner  in  which  the  coty- 
ledons are  disposed,  whether  the  seed  is  albuminous  or 
exalbuminous,  and,  if  the  latter,  how  the  reserve  of  food 
material  is  absorbed  by  the -growing  plant.  Careful 
attention  should  be  given  to  any  special  contrivances  to 
enable  the  young  plant  to  escape  from  the  seed-coat,  and 
the  existence  of  any  special  means  whereby  the  seed- 
coat  is  held  down  by  the  soil  while  the  young  plant  is 
being  withdrawn. 

Upon  examining  seed  beds  containing  germinating 
seeds,  it  may  often  be  noticed  that  a  few  of  the  young 
plants  do  not  germinate  properly.  They  may  fail  to  rid 
themselves  of  their  seed-coats  or  meet  with  other 
untoward  experiences.  These  cases,  in  particular, 


THE  SEED  21 

should  be  observed,  as  they  often  throw  considerable 
light  on  the  methods  of  germination  and  impress  the 
mind  with  the  importance  of  what  may,  at  first  sight, 
seem  trivial  and  unimportant  details. 

After  some  of  the  better  known  kinds  of  seeds  have 
been  studied,  much  instructive  information  may  be 
gained  by  collecting  seeds  of  wild  plants  and  studying 
their  methods  of  germination.  In  addition,  observations 
serving  to  develop  the  pupils'  powers  of  perception  and 
reasoning  may  be  made  upon  germinating  seeds  and 
seedlings  found  in  a  state  of  nature. 

The  following  list  of  seeds  for  study  is  merely 
suggestive ;  examples  should  be  selected  from  different 
parts  of  the  list,  and  the  seeds  should  not  be  studied 
in  the  order  in  which  they  are  arranged  : — 

Peas  and  Beans  Oak  (Acorn) 

Scarlet  Runner  Ash 

Haricot  or  Lima  Bean  Buckwheat 

Broad  Bean  Sycamore  or  Maple 

Garden  Pea  Marigold 

Sweet  Pea  Tomato 

Vetches  Barley 

Cabbage  .Wheat 

Radish  Maize 

Cress  Onion 

Cucumber  or  Marrow  Castor-oil 

Horse  Chestnut  Date  Palm 

Seeds  of  all  these  plants  can  be  easily  obtained.  In 
the  case  of  dates  the  seeds  from  the  fruit  as  sold  for 
eating  purposes  are  quite  good  ;  it  must  be  remembered, 
however,  that  they  take  several  months  to  germinate, 
preferably  in  a  pot  in  a  greenhouse  or  warm  room, 


22  NATURE  TEACHING 

Testing  Vitality  of  Seeds. 

The  following  method  of  testing  the  germinating 
power  or  vitality  of  seeds  is  easily  carried  out,  and  affords 
results  of  practical  value.  Pupils  should  test  the  vitality 
of  half  a  dozen  or  more  of  the  common  kinds  of  garden 
seeds  purchased  locally.  (These  experiments  should  be 
reserved  for  senior  pupils  and  advanced  classes.) 

"A  cheap  and  convenient  form  of  apparatus  for 
testing  the  vitality  of  seeds  at  home  is  the  following  :— 
Choose  two  earthenware  plates  of  the  same  size.  Cut 
out  two  circular  layers  of  flannel  somewhat  smaller  than 
the  plates.  Between  the  two  layers  place  100  seeds  of 
the  variety  to  be  tested.  Moisten  the  flannel  with  all 
the  water  it  will  absorb.  The  two  layers  of  flannel  are 
placed  in  one  plate  and  covered  with  the  other  and  set 
in  a  warm  place.  If  the  flannel  is  thin,  several  pieces 
should  be  used  in  order  to  absorb  sufficient  water. 
Other  kinds  of  absorbent  cloth  or  blotting-paper  can  be 
used,  but  thick  flannel  is  rather  more  satisfactory.  At 
the  Kansas  Experiment  Station  we  have  used  damp 
sand  for  a  seed  bed  with  good  success.  .  .  .  The  flannel 
should  be  kept  moist  by  the  addition  of  more  water 
when  necessary.  Some  seeds  will  commence  to  germi- 
nate on  the  third  day.  Each  day  an  examination  should 
be  made,  and  those  seeds  which  have  germinated  should 
be  recorded  and  removed.  For  practical  purposes,  two 
weeks  is  a  sufficient  time  for  the  test.  The  results 
obtained  may  be  considered  as  representing  the  per- 
centage of  vitality  under  favourable  conditions." 

"  Grass  seeds  require  as  much  as  three  weeks,  and 


THE  SEED  23 

seeds  of  some  trees  a  still  longer  time.  Beet  balls 
contain  from  three  to  seven  seeds.  With  very  small 
seeds  it  may  be  necessary  to  provide  for  the  circulation 
of  air  by  placing  small  pieces  of  wood  between  the 
layers  of  cloth  among  the  seeds.  With  most  varieties 
of  garden  plants  the  majority  of  seeds  should  germinate 
within  a  few  days  after  the  first  sprout  appears.  If  the 
period  of  germination  extends  over  a  longer  time  it 
shows  that  the  vitality  of  the  seed  is  low.  Seeds  of  the 
carrot  family  and  some  melon  seeds  may  not  show  as 
high  results  in  the  germinating  dishes  as  they  do  in  the 
ground." 

In   good   sound   seeds   the   following   numbers   per 
cent,  should  germinate  («): — 

(a)  From  Year-Book,  U.S.  Department  of  Agriculture,  1896. 

.  90  to  95 

.  80  „  85 

•  7o  „  75 

•  7o  „  75 

•  93  „  98 
.  90  „  95 
.  85  „  90 
.  90  „  95 
.  90  „  95 

*  Each  beet  fruit  or  "  ball "  is  likely  to  contain  from  three  to 
seven  seeds.     One  hundred  balls  should  give  at  least  1 50  sprouts. 


Barley 

.   .     90  to  95 

Oats  . 

Beans 

•     90  „  95 

Onion 

Beet  * 

150 

Parsley 

Cabbage     . 

.     90  to  95 

Parsnip 

Carrot 

.     80  „   85 

Peas  . 

Clover 

.     85   „   90 

Radish 

Cucumber  . 

.     85   „   90 

Tomato 

Lettuce 

.     85   „  90 

Turnip 

Mustard 

.     90  „   95 

Wheat 

CHAPTER    II 

THE   ROOT 

WE  have  already  seen  that  the  first  thing  to  make  its 
appearance  when  a  seed  germinates  is  the  root.  This 
is  at  first  usually  white  and  tender,  but  as  it  grows  older 
often  becomes  hard  and  woody,  and  covered  with  a 
brown  bark.  The  root  may  also  increase  in  thickness 
to  a  very  considerable  size. 

If  very  young  roots  are  examined  they  will  be 
found  to  be  clothed  with  fine  down  or  hairs  near  their 
extremities.  Owing  however  to  the  very  delicate 
character  of  these  fine  hairs-  it  is  not  always  easy  to  see 
them,  for  they  are  injured  if  the  root  is  at  all  roughly 
dealt  with.  These  hairs  may  be  seen  to  great  advantage 
on  the  roots  of  seedlings  of  barley,  Indian  corn,  etc., 
which  have  been  grown  in  a  moist  atmosphere.  On 
examining  such  a  root  it  will  be  noticed  that  the  tip 
and  the  portion  immediately  behind  it  is  quite  bare  and 
smooth ;  this,  as  we  shall  see  later,  is  the  growing 
region.  Then  follows  a  downy-looking  portion,  the 
character  of  which  is  due  to  the  presence  of  large 
numbers  of  minute  root-hairs ;  this  is  the  absorbing 
region.  The  older  portions  of  the  root,  like  the  youngest 

24 


THE  ROOT  25 

part,  are  completely  free  from  root-hairs.  When  a  very 
young  seedling  is  pulled  up  from  out  of  sandy  soil  it 
frequently  happens  that  a  considerable  quantity  of  sand 
remains  attached  to  the  root,  owing  to  the  root-hairs 
adhering  firmly  to  the  grains  of  sand  with  which  they 
were  in  contact. 

The  end  or  tip  of  a  root  is  soft  and  tender,  making 
one  wonder  how  so  delicate  a  structure  is  able  to  thrust 
itself  through  the  hard,  rough  soil.  Careful  examination 
will  show  that  the  tip  of  every  root  is  covered  with  a 
little  cap  or  shiejd  which  serves  to  protect  the  point 
from  injury.  This  root-cap  is,  in  many  plants,  not  very 
easy  to  see  without  the  use  of  a  lens,  but  may  often 
be  observed  in  roots  growing  in  water,  for  instance, 
those  of  the  frog's-bit,  duck-weed,  etc.  The  screw-pine 
(Pandanus),  to  be  seen  at  many  florists  and  in  almost 
every  botanic  garden,  throws  out  a  number  of  roots 
from  its  stem.  These  roots  grow  downwards  towards 
the  ground,  and,  if  their  tips  are  examined,  they  will  be 
found  to  be  covered  with  well  marked  root-caps.  These 
illustrate  remarkably  well  the  nature  of  the  appendage  to 
be  found  at  the  extremity  of  most  roots,  including  even 
their  finest  and  most  minute  branches. 

Roots  usually  grow  down  into  the  soil,  throwing  out 
numerous  branches,  and  permeating  the  soil  with  a 
network  of  fine  rootlets,  each  provided  with  root-hairs 
and  terminating  in  a  root-cap.  The  main  root  exhibits 
a  strong  tendency  to  grow  vertically  downwards,  in 
response  to  the  pull  of  gravity.  This  can  easily  be 
.proved  by  placing  a  growing  seedling  so  that  the  main 
foot  lies  horizontally.  If  this  is  done  it  is  found  that 


26  NATURE  TEACHING 

within  a  few  hours  the  end  of  the  root  bends  so  that 
once  again  the  tip  is  directed  vertically  downwards.  A 
simple  experiment  such  as  this  is  sufficient  to  show  that 
plants  are  not  mere  passive  living  things,  but  can 
control  the  movements  of  their  parts  almost  as  if  they 
possessed  senses  similar  to  those  of  animals. 

Roots  increase  in  length  by  the  addition  of  new 
material  at  their  ends  ;  the  older  parts  may  grow  in 
thickness,  but  they  do  not  increase  in  length.  Indeed, 
a  moment's  consideration  will  show  that  this  must 
necessarily  be  the  case,  for  if  roots  were  to  grow  in 
length  anywhere  but  at  their  ends  they  would  tear  off 
their  branches,  which  are  firmly  embedded  in  the  soil. 

Uses  of  Roots. 

Roots  have  several  uses  :  they  fix  the  plant  firmly  in 
the  soil,  they  absorb  water  together  with  the  nutriment 
which  plants  derive  from  the  soil  dissolved  in  it.  This 
absorption  of  water  is  only  effected  by  the  younger 
portions  of  the  roots  being  .practically  confined  to  the 
root-hairs.  The  region,  therefore,  which  bears  the 
root-hairs  is  the  absorbing  region,  and  this  fact  explains 
the  importance  of  the  young  roots  and  why  plants 
suffer  if  these  are  unduly  disturbed  or  injured.  The 
older  parts  of  the  root  have  no  power  of  themselves  to 
take  up  water  and  plant  food.  They  are  of  use  as 
mechanical  supports,  and  also  as  the  means  whereby 
the  water  taken  up  by  the  absorbing  region  is  passed 
on  to  the  stem  and  leaves  above  ground. 

Roots  frequently  act  as  storehouses  of  plant  food, 
particularly  in  the  case  of  biennial  plants.  Biennials 


THE  ROOT  27 

are  plants  which  require  two  years  to  complete  the 
cycle  of  their  lives.  They  usually  produce  during  the 
first  year  an  abundance  of  leaves  but  no  flowers.  These 
leaves  manufacture  plant  food,  in  the  form  of  starch  or 
sugar,  in  excess  of  the  plant's  immediate  needs,  and  this 
surplus  food  is  stored  away  in  the  roots  which  usually 
become  very  much  enlarged.  On  the  approach  of 
winter  the  leaves  die  down,  but  the  roots  remain  in  the 
ground  in  a  dormant  condition.  In  the  spring  of  the 
succeeding  year  the  plants  put  forth  new  leaves  and 
finally  flower  and  produce  seed,  and,  in  carrying  on 
these  processes,  the  store  of  food  in  the  roots  is 
drawn  upon  so  that  by  the  time  the  seeds  are  ripe  the 
roots  are  practically  exhausted.  After  the  seeds  have 
been  dispersed  the  plants  die.  This  condition  of  things 
may  be  well  seen  in  such  plants  as  beet,  carrot,  and 
turnip.  In  agriculture  man  takes  advantage  of  these 
plants  storing  up  food,  and,  collecting  the  roots  at  the 
end  of  the  first  year,  devotes  their  hoarded-up  food  to 
his  own  uses. 

The  observations  made  on  seedlings  have  shown 
that  the  roots  of  a  plant  usually  arise  from  the  radicle 
of  the  little  plant  in  the  seed.  In  many  plants,  however, 
roots  arise  not  only  in  this  manner  but  also  from  stems. 
A  good  example  is  the  ground  ivy,  which  puts  down 
little  bunches  of  roots  from  its  stem  as  it  trails  over  the 
ground.  It  is  obvious  that  these  roots  carry  on  the 
ordinary  work  of  absorption  of  water,  because  if  the 
main  root  dies  or  is  cut  away  the  plant  is  unaffected. 

In  some  plants  the  roots  formed  above  ground  are 
also  of  use  as  supports  ;  thus  in  the  Indian  corn  a  number 


28  NATURE  TEACHING 

of  roots  arise  from  the  stem,  at  some  distance  above  the 
soil,  grow  downwards  and  anchor  the  plant  firmly.  In 
the  screw-pine  such  roots  are  still  more  obvious,  and 
form  curious,  stilt-like  supporting  structures.  The  ivy 
furnishes  another  excellent  example  of  adventitious  roots 
borne  on  the  stem.  In  this  case  they  are  of  assistance 
to  the  plant,  supporting  it  when  climbing  up  trees,  walls, 
etc. 

In  the  case  of  many  plants,  a  portion  of  the  stem, 
separated  from  the  parent  plant,  so  that  it  no  longer 
receives  supplies  of  water  and  food,  shows  a  tendency  to 
attempt  to  save  its  life  by  producing  roots  of  its  own. 
In  this  effort  it  will  usually  be  successful  if  it  happens  to 
be  placed  in  a  moist  position.  A  piece  of  watercress 
placed  in  a  bottle  of  water  quickly  develops  a  number  of 
adventitious  roots.  Full  advantage  is  taken  of  this 
tendency  by  gardeners  and  agriculturists.  Many  orna- 
mental plants  are  propagated  in  this  way.  Pieces  of  the 
stem  are  cut  ofT  and  placed  in  moist  earth,  when  new 
roots  soon  make  their  appearance,  usually  from  near  the 
cut  end  of  the  stem,  and  a  new  plant  is  obtained.  Roses, 
geraniums,  chrysanthemums,  and  a  number  of  other 
.garden  plants  are  regularly  propagated  in  this  manner. 
.In  tropical  countries  this  method  of  propagation  is  used 
for  many  important  food  crops,  for  example,  sugar-cane, 
sweet  potato,  and  cassava  (the  source  of  tapioca). 

Nor  is  it  only  from  stems  that  roots  may  be  developed. 
Some  leaves,  when  plucked  from  their  parent  plant  and 
laic!  on  moist  soil,  will  throw  out  roots  and  leaf-buds,  so 
that,  in  a  little  time,  a  number  of  young  plants  may  be 
raised  from  a  single  leaf.  The  leaves  of"  fibrous-rooted  " 


THE  ROOT  29 

begonias  readily  form  roots  when  placed  under  suitable 
conditions,  and  are  commonly  propagated  in  this  way. 

Some  plants  grow  as  parasites  upon  other  kinds  of 
plants  ;  they  thrust  their  roots  into  the  stems  of  their 
hosts,  and  live  by  robbing  them  of  sap,  thus  weakening 
and  often  killing  the  plants  on  which  they  grow. 
Examples  of  parasitic  plants  are  the  strange,  thread-like 
yellow  dodders  (Cuscuta),  often  found  injuring  clover  and 
flax,  and  the  mistletoe  common  in  many  parts  of  Britain 
on  apple  and  other  trees.  The  method  by  which  this 
plant  spreads  from  tree  to  tree  is  interesting  (see  chapter 
on  Fruits). 

The  roots  of  these  parasitic  plants  have  no  .root-caps 
and  no  root-hairs,  these  structures  being  unnecessary 
under  the  peculiar  conditions  in  which  these  roots  grow. 
The  dodder  is  at  times  a  troublesome  pest  on  clover,  but, 
as  a  rule,  parasitic  plants  are  not  serious  enemies  to  the 
farmer  in  temperate  climates,  although  they  often  are  so 
to  the  tropical  cultivator  of  cocoa,  oranges,  etc. 

PRACTICAL  WORK 

Dig  up  several  germinating  seeds  and  young  seed- 
lings, and  examine  their  roots.  Good  examples  may  be 
obtained  by  sowing  beans,  peas,  barley,  wheat,  etc.,  at 
intervals  of  a  day  in  a  box  of  moist  sawdust  or  sand. 
Water  the  seeds  as  required.  In  warm  weather  they 
will  be  ready  in  about  a  week.  In  the  winter  a  few  days 
longer  will  be  required.  Observe  that  plants  with  two 
seed-leaves  put  out  a  main,  or  primary  root,  which  soon 
forms  numerous  branches  ;  on  the  other  hand,  plants 
with  only  one  seed-leaf  show  no  main  root,  but  a  number 


30  NATURE  TEACHING 

of  fine  roots  more  or  less  equal  in  size.  A  comparison 
of  the  root  systems  of  young  beans  or  peas  and  barley 
and  wheat  will  make  this  difference  clear.  Make  sketches 
of  all  the  seedlings  examined. 

Root-Hairs. 

Take  a  small  wooden  box,  place  at  the  bottom  two 
or  three  layers  of  wet  blotting-paper,  and  then  some 
barley  grains  which  have  been  soaked  in  water  for  about 
twelve  hours.  Cover  the  box  with  a  sheet  of  glass,  and 
put  it  on  one  side ;  examine  the  box  from  time  to  time, 
and  add  more  water  if  the  blotting-paper  should  become 
at  all  dry.  At  the  end  of  two  to  four  days,  according  to 
the  season  of  the  year,  root-hairs  should  be  present  in 
abundance,  and  there  should  be  no  difficulty  in  making 
out  the  characters  which  have  been  previously  described. 
Make  sketches  of  two  or  three  seedlings  of  different  ages, 
showing  exactly  the  position  of  the  root-hairs  in  each 
case. 

Pull  up,  very  carefully,  seedlings  which  have  been 
grown  in  sandy  soil ;  grains  of  sand  are  generally  found 
adhering  in  great  numbers  to  the  region  on  which  we 
now  know  the  root-hairs  occur.  Wash  off  this  sand  very 
carefully  by  gently  moving  the  roots  about  in  a  tumbler 
full  of  water.  Whilst  the  roots  are  suspended  in  the 
water,  examine  them  also  for  root-hairs.  Draw  a  seed- 
ling before  and  after  washing  the  sand  off. 

Root-Caps. 

Examine,  if  an  opportunity  occurs,  the  aerial  roots  of 
the  screw-pine,  and  observe  their  root-caps.  Then  look  for 


THE  HOOT  31 

similar,  but  much  smaller  and  more  delicate,  structures 
on  the  roots  of  other  plants,  such  as  pea  and  bean 
seedlings.  These  may  often  be  more  easily  seen  when 
the  roots  are  held  up  against  the  light,  and  a  magnifying 
glass  will  be  found  very  useful.  Examine  also  roots 
growing  in  water  ;  some  water-plants  have  no  root-caps, 
but  the  frog's-bit  (Hydrocharis\  if  obtainable,  furnishes 
good  examples,  as  also  do  the  duck-weeds  (Lemna\  so 
common  on  ponds.  These  roots  should  be  examined 
whilst  still  in  water,  Grow  seedlings  and  cuttings  in 
water,  and  examine  their  roots  for  root-caps. 

Make   simple    outline    drawings   of  all   the   plants 

examined. 

Growth  in  Thickness. 

The  youngest  part  of  a  root  is  usually  the  thinnest ; 
this  is  readily  seen  by  observing  any  of  the  seedlings 
already  obtained.  In  most  of  the  plants  which  have 
only  one  cotyledon  the  roots  soon  stop  growing  in 
thickness,  and  accordingly  all  the  older  roots  are  of 
a  uniform  size :  see  plants  of  barley,  wheat,  maize, 
grasses,  etc. 

In  dicotyledonous  plants,  on  the  other  hand,  increase 
in  thickness  may  go  on  for  a  very  long  time,  and  the 
roots  in  consequence  become  very  thick.  Take  any 
opportunity  of  observing  the  roots  of  trees,  for  instance, 
elm,  oak,  beech,  apple,  etc.  Good  examples  may  often 
be  seen  in  lanes  with  steep  banks,  where  the  roots  are 
frequently  left  exposed,  owing  to  the  soil  being  washed 
away.  The  main  roots  are  often  as  thick  as  the  main 
branches  of  the  stem.  Interesting  cases  showing  an 
enormous  increase  in  the  thickness  of  roots  can  readily 


32  NATURE  TEACHING 

be  seen  in  plants  of  radish,  turnip,   carrot,   and   beet 
These  plants  are  biennials  (see  page  26). 

Sow  a  few  seeds  of  radish,  turnip,  or  beet  in  a  garden 
bed,  or  in  a  box,  between  the  months  of  April  and  June. 
Towards  winter  the  leaves  die  down,  and  it  can  be  seen 
that  by  that  time  long  roots  have  been  formed  under- 
ground. The  roots  may  be  allowed  to  remain  in  the 
ground,  or,  if  more  convenient,  they  may  be  dug  up, 
labelled  and  stored  for  the  winter  in  a  moderately  warm 
dry  place,  where  they  run  no  risk  of  being  frozen.  In 
April  or  May  weigh  the  roots  and  plant  them  in  the 
ground  or  box  again,  and  water  as  required.  In  time 
new  leaves  should  be  formed,  to  be  followed  later  by 
flowers  and  seed.  When  the  seed  is  ripe,  collect  it  for 
future  use,  then  dig  up  the  roots,  dry  them  as  before,  and 
then  weigh  and  compare  their  weight  with  their  original 
weight  when  planted  in  the  spring.  The  roots  should,  of 
course,  be  marked  throughout  the  experiment  with  dis- 
tinctive numbers.  Careful  notes  should  be  made  of  the 
facts  observed,  also  of  the  character  of  the  roots  when 
planted  out,  and  after  the  plants  have  flowered.  Draw- 
ings are  very  important  to  show  the  changes  which  go 
on  in  the  roots. 

Growth  in  Length. 

Germinate  some  beans  in  moist  sand  or  sawdust,  and 
allow  them  to  grow  until  their  roots  are  about  two  inches 
long ;  wash  carefully  a  number  of  the  seedlings,  and 
select  one  which  has  a  straight,  well-formed  root,  perfectly 
free  from  injury. 

Lay  the  seedling  on  a  piece  of  damp  blotting-paper, 


THE  ROOT 


33 


and,  alongside  it,  a  piece  of  cardboard,  so  arranged  that 
the  surfaces  of  root  and  cardboard  are  on  the  same  level. 
With  a  fine  camel's  hair  brush  and  Indian  ink  make  a 
number  of  fine  lines  on  the  root,  and  a  corresponding  set 
on  the  cardboard,  commencing  as  close  to  the  tip  of  the 
root  as  possible,  and  continuing  them  backward  for  about 
one  inch.  These  lines  should  not  be  more  than  £th  inch 


FIG.  i.  — Mode  of 
measuring  growth 
in  length  of  the 
root  of  a  germinat- 
ing bean. 


FlG.  2. — Germinating  bean 
fixed  in  a  glass  jar  by 
means  of  a  pin  passing 
through  the  cork.  The 
root  is  marked  into  equal 
transverse  divisions  at  the 
beginning  of  the  experi- 
ment. After  a  period  of 
about  twenty-four  hours 
the  region  of  most  active 
growth  may  be  ascertained. 


apart,  and  in  marking  them  great  care  must  be  taken  not 
to  injure  the  root.  Place  each  bean  in  a  thistle-funnel 
standing  upright  in  a  tumbler  or  bottle  of  water,  and 
cover  the  top  of  the  funnel  with  a  watch  glass,  or  small 
piece  of  wood  (see  Fig.  i). 

As  an  alternative  method,  pin  the  seedling,  with  the 
root  hanging  vertically,  on  the  inside  of  a  box  or  bottle, 
the  atmosphere  in  which  is  kept  moist,  as  in  the  experi- 

C 


34  NATURE  TEACHING 

ment  with  germinating  barley.  The  best  method  of 
fastening  the  seedlings  is  to  pass  an  ordinary  pin  through 
the  two  cotyledons,  taking  care  not  to  injure  the  young 
stem  or  root  (see  Fig.  2). 

Examine  after  twenty- four  hours,  comparing  the 
marks  on  the  root  with  those  on  the  card. 

It  should  be  found  that  the  first  one  or  two  divisions, 
near  the  tip,  have  not  altered  in  length ;  that  the  next 
ones  have  grown  a  great  deal ;  while  those  still  further 
back  have  remained  stationary  like  those  at  the  tip. 
Make  a  drawing  of  a  root  as  first  set  up,  with  the  marks 
at  equal  distances,  and  after  one,  two,  and  three  days, 
showing  exactly  the  position  of  the  marks  at  each  of 
these  times. 

From  this  simple  experiment  we  learn  that  in  a 
root  the  greatest  amount  of  growth  is  not  at  the 
apex,  but  some  little  way  behind  it,  so  that  the  root- 
tip  protected  by  its  root-cap  is,  as  it  were,  driven 
down  through  the  soil  by  the  rapid  growth  of  the 
portion  just  behind  it. 

Absorption  by  Roots. 

Take  two  small  bottles  having  short,  narrow  necks, 
and  fill  both  with  water.  To  one  add  a  few  drops  of 
eosin  solution  or  a  little  red  ink,  just  enough  in  either 
case  to  colour  the  .water  distinctly  red.  To  the  second 
bottle  add  a  little  carmine  which  has  been  previously 
rubbed  to  a  thin  paste  with  water.  Take  two  seedlings, 
such  as  those  previously  examined  for  root-hairs  (p.  30), 
and  fix  one  in  each  bottle  so  that  its  roots  are  immersed 
in  the  liquid.  This  may  be  done  by  wedging  them 


THE  ROOT  35 

in  position  with  some  cotton-wool.  After  a  day  or  so 
remove  the  seedlings,  and  gently  wash  them  in  some 
clean  water  to  remove  any  colouring  matter  on  their 
outside.  Then  cut  them  lengthwise  and  across.  Note 
that  the  one  placed  in  the  weak  eosin  or  red  ink  has 
become  red  inside,  whilst  the  one  from  the  carmine  has 
not.  The  explanation  of  this  difference  is  to  be  found 
in  the  fact  that  eosin  and  red  ink  are  soluble  in  water, 
whilst  carmine  is  not,  but  remains  in  the  water  as  very 
fine,  solid  particles.  The  red  solution  can  pass  into  the 
roots,  but  it  is  not  possible  for  any  solid  particles,  how- 
ever small,  to  make  an  entry. 

This  experiment  has  a  very  important  bearing  on 
the  question  of  the  relative  value  of  manures  and  other 
forms  of  plant  food. 

Roots  and  Gravitation. 

Take  a  wide-mouthed  square  bottle  of  clear  glass  (for 
instance,  a  sweet-bottle)  and  pour  in  it  a  small  quantity 
of  water.  Obtain  a  good  cork  to  fit  the  bottle,  and  pass 
through  it  a  fine  knitting-needle.  Take  a  bean  which 
has  been  allowed  to  germinate  in  damp  sand  or  sawdust, 
and  has  a  root  about  one  inch  long,  and  fix  it  on  the  end 
of  the  knitting-needle  so  that  its  root  points  downwards. 
Place  the  cork  with  the  bean  in  the  bottle,  and  allow  it 
to  remain  for  twelve  hours.  The  root  continues  to 
grow  straight  downwards.  Now  lay  the  bottle  on  its 
side,  when  the  root  will  lie  horizontally.  Examine  at 
frequent  intervals  (for  instance,  of  two  hours),  and  note 
that  the  direction  of  the  root  changes,  the  tip  soon 
curving  round  until  it  comes  to  point  vertically  down- 


36 


NATURE  TEACHING 


wards.  The  position  of  the  bottle  may  now  be  changed 
again,  and  once  more  the  root  will  be  found  to  bend 
round  into  the  vertical  position. 

A  round  bottle  will  serve  almost  as  well,  but  care 
must  then  be  taken  to  prevent  it  rolling. 

Another  simple  and  equally  serviceable  method  is 
to  use  a  box  with  a  movable  front.  The  atmosphere 


FIG.  3. — Germinating  beans  fixed  on  the  sides  of  a  box  with 
a  removable  glass  front.  The  beans  are  fixed  with  their 
roots  pointing:  in  different  directions,  but  at  the  end  of  a 
few  hours  the  tips  of  both  roots  will  be  seen  to  have 
curved  round  until  they  come  to  point  vertically  down- 
wards. 


in  the  box  should  be  kept  damp  by  means  of  wet 
sponges.  Pin  the  seedling  bean  to  the  back  of  the  box, 
and  turn  the  box  into  various  positions,  as  in  the  case 
of  the  bottle  (see  Fig.  3). 

Careful  drawings  should  be  made  showing  the 
position  of  the  root  at  first,  and  at  intervals  after  the 
bottle  or  box  has  been  turned  round. 


THE  ROOT  37 

Roots  and  Water. 

Sow  some  peas  in  an  ordinary  sieve  filled  with 
damp  sawdust,  and  hang  the  sieve  up.  The  roots  of 
the  seedlings  grow  down  in  the  ordinary  way,  and  at 
length  project  through  the  meshes  of  the  sieve.  Then, 
however,  they  usually  change  their  course,  and  turning 
horizontally,  they  creep  along  the  underneath  surface 
of  the  sieve,  or  even  grow  vertically  upwards  into  the 
damp  sawdust.  The  attraction  of  the  roots  for  water 
here  overcomes  their  tendency  to  grow  downwards. 

Make  careful  drawings  of  the  apparatus,  and  of  the 
results  noticed. 

Propagation  by  Cuttings. 

It  is  convenient  to  grow  small  cuttings  in  boxes  and 
to  transplant  them  afterwards  into  garden  beds.  Boxes 
for  this  purpose  are  prepared  in  the  same  manner  as 
boxes  for  seed  planting,  but  it  is  desirable  to  use  either 
sand  or  very  sandy  soil. 

Having  prepared  a  box,  proceed  to  plant  cuttings  of 
such  plants  as  roses,  geranium,  willow,  lilac,  or  coleus. 
Ascertain  from  a  gardener  what  cuttings  "  strike  "  easily. 
Select  a  branch  which  is  fairly  firm  and  woody,  but  not 
too  young  and  soft.  Cut  it  into  pieces  of  4  to  6  inches 
in  length,  making  the  cut  at  the  lower  end  close  below  a 
node  or  joint,  as  it  is  from  the  nodes  that  roots  arise  in 
the  largest  numbers.  Cut  off  most  of  the  foliage  in 
order  to  reduce  the  loss  of  water  which  takes  place  from 
leaf  surfaces  (see  chapter  on  leaves),  and  place  the 
cuttings  in  the  soil,  embedding  them  to  a  depth  of  from 


38  NATURE  TEACHING 

two  to  three  inches.  Compress  the  soil  firmly  around 
the  cuttings,  for  if  the  soil  remains  loose  the  cutting  will 
suffer  from  lack  of  moisture.  The  work  of  planting 
cuttings  is  much  facilitated  by  using  a  piece  of  wood 
about  six  inches  long  and  about  the  thickness  of  one's 
little  finger  for  making  the  hole  in  the  soil  to  receive  the 
cutting,  and  for  compressing  the  soil  around  its  base. 
Water  and  tend  the  boxes,  as  in  the  case  of  seeds. 

Plant  a  number  of  cuttings  so  as  to  provide  material 
for  examination.  At  short  intervals  remove  one  or 
more  cuttings  from  the  soil,  and  note  carefully  the 
changes  which  have  taken  place ;  these  examinations 
should  continue  until  the  relationship  of  the  resulting 
new  plant  to  the  cutting  is  clearly  established.  Sketches 
or  diagrams  should  accompany  all  the  notes. 

Place  cuttings  of  watercress  and  coleus  in  bottles  of 
water.  After  a  time,  roots  will  develop,  and  their  growth 
and  character  may  be  observed.  It  is  convenient  to  use 
a  clear  bottle  wrapped  round  with  paper  or  cloth  to 
exclude  the  light. 

Branches  of  shrubs  will  frequently  take  root  if  they 
are  fastened  down  on  moist  soil.  By  means  of  suitable 
pegs,  secure  two  or  three  branches  of  a  rose,  or  other 
tree,  firmly  upon  the  ground,  covering  them  with  a  little 
soil  where  they  touch  the  ground  ;  water  and  tend  care- 
fully. The  branch  will  after  a  time  be  found  to  have 
rooted,  and  may  then  be  severed  from  the  parent  tree  and 
planted  in  another  spot.  Rooting  may  be  encouraged 
in  this  operation  by  removing  a  narrow  ring  of  bark  at 
the  place  where  the  branch  touches  the  ground. 

When  valuable  trees  are  to  be  propagated,  and  it  is 


THE  ROOT 


39 


important  that  no  risk  be  run  of  the  cutting  dying,  the 

last  plan  may  be   modified  as  follows.     On  the  rose, 

gooseberry,  lilac,  or  other  shrub  which  it  is  desired  to 

propagate,  select  a  branch  which  is  easily  accessible,  and 

from  it  remove  a  ring  of  bark,  right  round  the  stem,  about 

half  an  inch  in  width.     Have  ready  a  flower-pot,  sawn 

lengthways  into  halves,  or  a  small  wooden  box  with  one 

side    removed   and    a   slot    in    the 

bottom    to    admit    the    branch,   as 

shown  in  Fig.  4.     Place  the  pot  in 

position  round  the   stem  where  it 

has   been  prepared,  bringing    that 

part  of  the   stem   from   which  the 

bark    has  been  removed,  to  about 

the   middle   of  the    pot     Tie    the 

two  halves  of  the  pot  together,  and 

secure   it   firmly   in    its    place    by  FIG.  4.— Box   with   top 

.          .  .  and  one  side  removed, 

fastening  it  to  a  stake  driven  in  and  slot  cut  in  bottom 
the  ground.  Everything  being  now  Skl^top.25? 
in  position,  put  a  little  dried  grass 
or  coco-nut  refuse  at  the  bottom  of 
the  pot  and  fill  up  with  soil ;  keep 
the  pot  watered.  After  the  branch  has  been  for  some 
time  in  the  pot,  begin  the  process  of  severing  it  from  the 
parent  plant  by  cutting  a  small  notch  in  it  a  few  inches 
below  the  bottom  of  the  pot ;  after  three  or  four  days 
deepen  this  notch  and  repeat  the  process  at  intervals 
until  complete  severance  is  effected.  The  branch  should 
now  have  rooted  and  become  an  independent  plant  which 
may  be  planted  in  a  suitable  place. 

Peg  down  on  moist  sand  some  leaves  of  "fibrous 


and  the  box  filled  with 
soil  the  front  should  be 
slid  in  along  grooves  in 
the  sides. 


40  NATURE  TEACHING 

rooted"  begonias,  the  veins  of  which  have  first  been 
nicked  on  the  lower  side  with  a  penknife.  The  pot  or 
box  should  be  covered  with  a  sheet  of  glass,  and  lightly 
watered  occasionally  as  found  necessary.  In  the  course 
of  a  week  or  two  roots  will  begin  to  be  formed  at  the  cut 
places,  and  rough  wart-like  outgrowths  to  appear  on  the 
upper  side.  From  these  small  leaves  are  later  formed, 
and  develop  into  little  plants.  This  method  is  employed 
for  the  propagation  of  these  plants,  and  is  of  especial 
interest  in  showing  that  in  some  plants,  at  any  rate,  roots 
and  even  complete  plants  are  formed  by  leaves. 


CHAPTER  III 

THE   STEM 

IN  the  previous  chapter,  although  attention  has  mainly 
been  directed  to  the  root,  it  can  scarcely  have  escaped 
notice  that  most  of  the  plants  examined  are  made  up  of 
two  well-marked  and  very  distinct  portions — (i)  the 
underground  root,  and  (2)  the  aboveground  stem  bear- 
ing leaves  and  flowers,  and  often  for  convenience  spoken 
of  as  the  "  shoot." 

It  is  true  that  in  some  plants — for  example,  the  house- 
leek  and  primrose — the  stem  is  exceedingly  short,  so  that 
the  leaves  appear  to  spring  almost  directly  from  the 
ground.  In  other  cases,  for  instance,  in  climbing  plants 
such  as  the  hop,  scarlet  runner,  etc.,  the  stems  are  very 
long  and  thin,  and  the  same  holds  good  for  many  creep- 
ing plants  like  the  couch  grass. 

Stems  also  vary  greatly  in  another  respect.  Whilst 
young  they  are  almost  all  soft  and  green  ;  some  remain 
permanently  in  this  condition,  but  others  become  hard 
and  woody  with  age.  The  comparison  of  young  and  old 
shoots  of  elder,  and  young  and  old  garden  balsams  illus- 
trate this  point  very  well.  Putting  aside  for  the  moment 
all  these  differences,  we  may  say  that  plants  in  general 

41 


42  NATURE  TEACHING 

are  made  up  of  the  underground  root,  and  the  above- 
ground  shoot  bearing  leaves,  flowers,  and  fruit  Root 
and  shoot  are  distinct  even  whilst  the  young  plant  is 
still  contained  in  the  seed,  being  represented  there,  as  we 
have  learnt,  by  radicle  and  plumule  respectively. 

The  leaves  are  usually  arranged  on  the  stem  in  a 
definite  manner ;  the  places  on  the  stem  from  which  the 
leaves  spring  are  known  as  \hzjoints  or  nodes,  and  the 
interval  between  any  two  nodes  is  an  internode.  Nodes 
and  internodes  may  be  very  clearly  distinguished  on 
most  growing  shoots,  e.g.,  roses,  elder,  privet,  etc. 

On  examining  any  leaf-bearing  stem  it  will  be 
noticed  that  the  oldest  leaves  are  at  the  base,  and  that 
as  we  approach  the  summit  of  the  stem  the  leaves  get 
younger  and  younger.  At  the  apex  itself  we  find  the 
youngest  leaves,  often  more  or  less  closely  packed 
together  to  form  a  leaf-bud.  Similar  but  smaller  leaf- 
buds  are  usually  to  be  found  lower  down  the  stem, 
situated  just  above  the  place  where  a  leaf  joins  the  stem  ; 
it  is  very  general  to  find  one  to  each  leaf. 

In  the  majority  of  plants  the  stem  is  the  above- 
ground  portion,  the  root  only  being  below  ground. 
This,  however,  is  not  always  the  case,  and  a  few  of  the 
more  important  exceptions  will  be  considered  later. 

Uses  of  Stems. 

One  of  the  most  important  functions  of  the  stem  of 
a  plant  is  to  support  the  leaves  and  display  them  to  the 
air  and  light  in  the  best  possible  manner  for  the  work 
they  have  to  do.  Careful  observations  should  be  made 
of  the  arrangement  of  the  leaves  on — (i)  upright  grow- 


THE  STEM  43 

ing  plants ;  (2)  climbers  against  walls,  trees,  etc. ;  (3) 
plants  which  trail  along  the  ground  ;  (4)  plants  in  which 
some  of  the  branches  are  upright  whilst  others  lie  more 
or  less  horizontally.  The  privet  may  be  taken  as  a 
good  example  of  the  last  class.  On  the  upright  grow- 
ing shoots  the  leaves  are  arranged  all  round  the  stem, 
so  that  we  cannot  say  which  is  the  upper  and  which 
the  lower  side  of  the  shoot.  If,  however,  we  examine 
a  shoot  growing  horizontally,  we  at  once  notice  that  all 
the  leaves  are  twisted  round  to  one  side,  so  that  on 
looking  from  above  we  see  only  the  upper  sides  of 
leaves,  whilst  from  beneath  only  the  under  sides.  Here, 
then,  we  have  apparently  a  distinct  upper  and  lower 
side  to  the  branch.  Still  more  careful  examination, 
however,  particularly  of  the  tip  of  the  same  branch, 
will  show  that  the  leaves  arise  exactly  as  on  the 
upright-growing  shoots,  and  twist  later  into  their  final 
positions.  Many  creeping  plants — e.g.,  ground  ivy, 
creeping  jenny,  etc. — also  show  very  nice  arrangements 
to  prevent  the  leaves  shading  one  another,  and  in  the 
practical  work  great  attention  should  be  paid  to  them. 

Stems,  like  roots,  often  serve  as  storehouses  of  food. 
The  majority  of  the  stems  which  serve  as  storehouses 
grotf  partially  or  entirely  beneath  the  surface  of  the  soil, 
probably  to  protect  the  valuable  stores  of  food  they 
contain  from  injury  and  cold.  In  general  appearance 
these  underground  stems  resemble  roots,  indeed  in  some 
cases  it  is  difficult  to  distinguish  them  from  roots.  It 
may,  however,  be  taken  as  a  general  rule  that  a  stem- 
whatever  use  it  may  serve — always  bears  leaves.  The 
examination  of  the  examples  given  below  will  show  us 


44  NATURE  TEACHING 

that  we  do  not  find  green  leaves  in  every  case,  as  in 
underground  stems  the  leaves  are  more  commonly 
reduced  to  dry,  scale-like  bodies. 

The  iris  or  flag,  and  Solomon's  seal  afford  good 
examples  of  stems  of  this  kind,  running  horizontally  in 
the  ground,  bearing  scale  leaves,  leaf-buds,  and  roots. 
Stems  of  this  nature  are  usually  spoken  of  as  rJiizomes. 
Those  leaf-buds  which  grow  above  the  surface  of  the 
soil  form  green  leaves,  but  the  underground  portion  of 
the  stem  bears  nothing  but  dry  scales. 

A  potato  is  an  enlarged  and  swollen  stem,  and  not  a 
root.  Leaves  are  almost  absent,  being  represented  only 
by  the  "  eyes?  which  are  in  reality  leaf-buds,  as  is  easily 
seen  by  keeping  some  potatoes  in  a  damp  place  for  a 
time,  when  the  "  eyes  "  will  grow,  developing  finally  into 
well-marked  stems  bearing  leaves.  Stems  of  the  nature 
of  the  potato  are  known  as  tubers.  The  Jerusalem 
artichoke  is  interesting,  as  its  underground  stem,  with 
its  very  well-marked  scale  leaves,  serves  to  connect  up 
the  type  of  stem  met  with  in  the  iris  and  Solomon's  seal, 
and  true  tubers,  such  as  the  underground  potato  stems. 

Rhizomes  and  tubers  are  examples  of  stems  which 
are  adapted  to  a  special  purpose,  namely,  to  hold  stores 
of  food  for  the  future  use  of  the  plant. 

In  the  iris  the  underground  stem  keeps  on  growing, 
year  after  year,  and  by  its  branching  serves  also  to  pro- 
pagate the  plant,  for,  as  the  older  portions  die  away,  the 
branches  become  separated  and  form  independent  plants. 
In  the  potato  this  is  still  more  marked,  each  potato  plant 
forming  each  year  a  large  number  of  tubers,  every  one 
of  which  can  the  next  year  form  one  or  more  new  potato 


THE  STEM  45 

plants.  As  is  the  case  of  roots,  so  with  stems,  man  puts 
some  to  his  own  use,  and  accordingly  cultivates  potato 
plants  and  allows  them  to  form  their  tubers,  or  stores  of 
food,  which  he  utilises. 

Stems  also  serve  as  the  means  whereby  plants  climb. 
In  some  cases — for  instance,  convolvulus  and  beans — the 
ordinary  stem  twines  about  any  convenient  support ;  in 
others — for  example,  the  white  bryony,  passion  flower, 
grape  vine,  etc. — portions  of  the  stem  are  modified  to 
form  special  climbing  organs,  known  as  tendrils. 

The  crocus  affords  another  example  of  a  stem  acting 
as  a  storehouse  of  food.  The  stem  is  here  even  more 
specialised  than  the  potato,  and,  as  we  shall  see  later, 
contains  not  only  a  store  of  food,  and  leaf-buds,  but 
even  the  flowers  which  will  come  up  in  the  spring  after 
it  is  formed,  the  whole  being  packed  up  in,  and  pro- 
tected by,  special,  tough,  scale  leaves. 

It  is  of  great  interest  to  trace  how  what  appear  at 
first  sight  very  different  and  distinct  plant  structures  are 
really  very  much  alike,  and  gradually  pass  into  one 
another. 

In  the  creeping  jenny  and  many  other  plants  we  find 
stems  which  trail  over  the  surface  of  the  ground  but 
bear  leaves  all  along  their  length.  In  the  strawberry 
these  ordinary  creeping  stems  bearing  leaves  are 
replaced  by  runners,  with  only  small  scale  leaves.  This 
type  is  the  best  for  the  special  work  they  perform  of 
spreading  the  plant  from  place  to  place.  In  the  iris 
and  Solomon's  seal,  underground  stems  loaded  with 
food-reserve  take  the  place  of  the  strawberry  runners. 
The  artichoke  supplies  the  connecting  link  between  the 


46  NATURE  TEACHING 

rhizome  and  the  potato  tuber ;  and  finally  we  get  the 
crocus  corm,  a  very  compact,  stem  structure  containing 
food-leaf  and  flower-buds,  with  a  protective  covering. 

Structure  of  Stems. 

A  piece  of  the  stem  of  a  horse  chestnut,  elm,  oak,  ash, 
hawthorn,  rose,  or  other  tree,  when  cut  across  and  ex- 
amined, is  seen  to  be  composed  of  various  parts  arranged 
in  a  definite  manner.  In  the  middle  there  is  a  soft 
portion,  the  pith,  small  in  some  cases,  large  in  others ; 
this  is  surrounded  by  hard  wood,  which,  in  the  case  of 
old  trees,  makes  up  the  greater  portion  of  the  stem, 
whilst  in  young  branches  it  only  forms  a  thin  ring ;  out- 
side of  all  is  the  bark,  sharply  marked  off  and  easily 
separable  from  the  wood.  The  bark  itself  is  made  up 
of  three  layers  (easily  recognised  in  the  horse  chestnut 
or  ash) — an  inner,  fibrous  layer;  a  middle,  green  portion; 
and  an  outer,  thin  brown  layer,  not  at  all  fibrous,  but 
which  readily  breaks  in  pieces  if  any  attempt  is  made 
to  detach  it. 

The  region  where  wood  and  bark  join  is  of  great 
importance,  for  there  is  present,  between  these  two 
conspicuous  tissues,  a  soft,  somewhat  slimy,  thin  layer, 
best  seen  in  young,  vigorously-growing  shoots.  This 
layer  is  the  cambium,  or  growing  layer,  and  consists  of 
young  growing  tissue  similar  to  that  which  is  present  at 
the  apices  of  stems  and  roots.  The  cambium  has  the 
power  of  producing  new  tissue  in  either  direction ;  that 
is  to  say,  situated  as  it  is  between  wood  and  bark,  it  can 
add  both  to  the  wood  and  to  the  inner  bark.  The 
increase  in  thickness  of  the  wood  is  generally  very  much 


THE  STEM  47 

more  than  that  of  the  bark.  This  is  well  seen  by  ex- 
amining the  cut  end  of  a  felled  tree,  for  instance,  an  elm 
or  oak  ;  the  enormous  difference  in  thickness  between 
such  an  old  tree  and  a  seedling  elm  or  oak  being  due 
almost  entirely  to  the  additions  made  to  the  wood  by 
the  activity  of  the  cambium  layer.  The  presence  of  a 
cambium  is  practically  restricted  to  dicotyledonous 
plants. 

Certain  changes  take  place  in  the  wood  of  many 
trees  as  it  increases  in  age.  From  what  has  already 
been  said,  it  will  be  recognised  that  the  oldest  wood  is 
near  the  centre,  the  new  wood  being  formed  always  on 
the  outside.  It  is  not  uncommon  to  find  the  wood  near 
the  centre  of  the  trunk  darker  in  colour.  This  is  par- 
ticularly well  seen  in  the  laburnum,  where  the  centre 
part  is  deep  brown  and  the  outer  portion  light  yellow. 
The  elm,  oak,  etc.,  show  the  same,  although  to  a  less 
striking  degree.  This  central  dark  wood  is  the  heart- 
wood,  and  the  outer  softer  and  lighter-coloured  wood 
the  sapwood. 

The  rate  of  formation  and  the  character  of  the  new 
wood  formed  from  the  cambium  varies  at  different 
season's  of  the  year.  Thus,  when  a  cross-section  of  a 
stem  is  looked  at,  rings  or  layers  in  the  wood  are  visible. 
Trees  grown  in  countries  having  well-marked  seasons 
of  winter  and  summer,  usually  show  a  definite  ring  for 
each  year's  growth,  and  by  counting  the  rings  the  age 
of  the  tree  can  be  told.  In  tropical  countries  the  seasons 
are  often  not  sharply  marked  off,  and  the  rings  of  growth 
are  accordingly  often  wanting  or  indistinct. 

Close  examination  of  a  cross-section  of  a  stem  reveals 


48  NATURE  TEACHING 

the  presence  of  fine  lines — well  seen  in  a  rose  stem — 
running  through  the  wood,  joining  up  pith  and  cambium. 
They  are  also  well  indicated  by  radiating  cracks,  often 
formed  in  posts  or  felled  timber  which  has  been  exposed 
to  the  weather  for  some  time.  These  are  the  medullary 
rays  which  serve  to  connect  up  and  maintain  com- 
munication between  the  various  parts. 

If  now  a  stem  of  maize,  cane,  or  almost  any  other 
monocotyledonous  plant  is  examined,  the  parts  will  be 
seen  to  be  arranged  in  a  very  different  manner  from 
those  of  the  stems  already  studied.  In  the  stems  of 
this  second  set  we  can  distinguish  no  pith,  no  ring  or 
column  of  wood,  no  separable  bark,  and  no  cambium. 
They  exhibit  in  cross-section  a  groundwork  of  soft 
tissue,  in  which  harder  portions  are  irregularly  scattered  ; 
and  whilst  the  outer  portion  forms  a  kind  of  rind,  it  is 
not  essentially  different  from  the  rest,  but  merely  con- 
tains a  much  greater  proportion  of  the  hard  portions, 
and  very  little  of  the  soft  ground-tissue.  On  cutting 
such  a  stem  lengthwise,  it  is  readily  seen  that  the  hard 
portions  are  in  reality  fibrous  strands  which  run  through 
the  stem. 

For  a  full  description  of  the  various  tissues  compos- 
ing these  two  types  of  stems,  the  reader  is  referred  to 
botanical  text-books. 

Grafting  and  Budding. 

The  existence  of  the  cambium  in  the  stems  of  dicotyle- 
donous plants  renders  possible  the  carrying  out  of  certain 
operations  known  as  grafting  and  budding.  This 
depends  upon  the  fact  that  the  cambium,  being  a  region 


THE  STEM  49 

of  active  growth  where  new  tissue  is  being  regularly 
formed,  can  repair  injuries  to  the  bark  or  to  the  surface 
of  the  wood,  and,  moreover,  when  the  cambiums  of  two 
stems  are  brought  together  by  suitable  operations,  they 
both  form  new  tissues  so  intermingled  that  the  two  stems 
unite  and  grow  together. 

To  carry  out  grafting  in  its  simplest  form,  select  two 
branches,  of  equal  thickness,  of  different  trees  of  the 
same  species,  and  without  separating  either  from  its 
parent,  cut  away  a  portion  of  the  bark  and  a  little  of  the 
wood  below  it,  thus  exposing  the  cambium  as  a  narrow 
line  surrounding  the  cut ;  take  care  to  make  the  cuts  on 
both  branches  of  about  the  same  size  and  shape.  Bring 
the  cut  surfaces  together  with  their  respective  cambiums 
in  close  contact  as  far  as  possible,  and  securely  bind  the 
branches  together  in  this  position.  Each  cambium  now 
makes  efforts  to  repair  the  injuries  to  the  surrounding 
tissues,  and,  all  being  well,  the  new  growth  thus  resulting 
unites  the  two  branches.  One  of  the  branches  may  now 
be  severed  from  its  parent  tree  at  a  place  between  the 
root  and  the  point  of  grafting.  The  upper  part  of  the 
branch  so  severed  will  have  to  depend  on  the  root  of  the 
other  tree  for  its  support,  and  thus  becomes  a  part  of  that 
tree,  or,  as  it  is  usually  expressed,  is  grafted  on  to  it. 
This  method  of  grafting  is  known  as  "grafting  by 
approach"  because  the  two  plants,  each  on  its  own  roots, 
are  brought  together. 

In  other  forms  of  grafting,  separate  pieces,  called  scions, 
of  the  tree  which  it  is  desired  to  propagate,  are  fixed,  with 
proper  precautions,  to  another  tree  of  the  same  species, 
known  as  the  stock,  properly  prepared  to  receive  them. 

D 


50  NATURE  TEACHING 

In  all  the  methods  the  essential  point  is  that  the  cambium 
of  the  scion  shall  be  brought  into  contact  with  the  cam- 
bium of  the  stock ;  any  mode  of  cutting  or  shaping  the 
cut  surfaces  of  the  stock  and  scion  which  enables  this 
contact  of  the  cambiums  to  be  secured  may  be  adopted 
as  a  method  of  grafting,  and  the  methods  are  often 
named  according  to  the  manner  in  which  the  scion  and 
stock  are  cut  or  shaped.  The  branch  or  stem  which  is  to 
serve  as  the  stock  is  cut  off  at  the  place  where  it  is 
desired  to  insert  the  scion,  and  shaped  according  to  the 
method  to  be  adopted.  In  the  simplest  case  the  stock 
is  cut  across  obliquely,  and  a  scion  of  the  same  thickness 
is  cut  in  a  similarly  oblique  manner,  so  that  the  two  cut 
surfaces  will  fit  together.  Stock  and  scion  being  thus 
prepared,  fit  them  together,  so  that  their  cambiums  are 
in  close  contact,  and  fasten  them  securely  in  position  by 
means  of  suitable  binding  material.  There  is  a  tendency 
for  scions  thus  shaped  to  slip  out  of  position ;  notches 
or  tongues  are  therefore  often  cut  in  both  stock  and  scion 
to  diminish  this  danger  of  slipping,  but  care  must  be 
taken  to  cut  the  two  surfaces  in  such  a  manner  that  they 
may  fit  together  accurately. 

In  some  cases  it  is  desired  to  fix  a  small  scion  on  a 
large  stock.  The  stock  is  then  cut  off  at  the  place  where 
the  scion  is  to  be  inserted,  the  end  of  the  scion  trimmed 
to  a  thin,  pointed,  wedge-like  form,  and  thrust  in  between 
the  wood  and  the  bark  of  the  stock — into  the  cambium  in 
fact.  In  another  method  a  long  narrow  V"snaPe<^  incision 
is  made  in  the  bark  and  down  into  the  wood  of  the  stock, 
the  base  of  the  scion  is  cut  to  a  corresponding  shape,  fitted 
to  the  stock  and  secured  in  position  by  binding, 


THE  STEM  51 

In  all  these  methods  of  grafting  it  is  necessary  to 
cover  the  junction  between  scion  and  stock  in  order  to 
prevent  the  tissues  drying,  for  the  cambium  would  then 
die  and  no  union  take  place.  In  order  to  preserve  the 
tissues  in  a  moist  condition  it  is  sometimes  the  custom 
to  fix  a  mass  of  clay  over  the  place  where  stock  and 
scion  meet ;  this,  however,  is  liable  to  become  dry  and  to 
crack,  so  that  it  is  preferable  to  employ  soft  wax  in  a 
similar  manner.  More  commonly,  strips  of  cloth  or 
tape  are  covered  with  the  wax,  and  these  strips  are 
bound  round  the  joint,  thus  holding  the  scion  in  place, 
and,  at  the  same  time,  forming  a  waterproof  covering 
which  effectually  keeps  the  tissues  from  drying. 

One  particular  method  of  grafting,  known  as  budding, 
deserves  special  mention.  It  consists  in  the  removal  of 
a  bud  together  with  a  little  of  the  wood  and  bark,  and 
consequently  a  portion  of  the  cambium,  from  one  plant, 
and  its  insertion  under  the  bark,  that  is  in  the  cambium 
region,  of  another  plant  The  inserted  bud  unites  with 
the  plant  in  which  it  is  inserted,  and,  growing  quickly, 
forms  a  new  branch. 

When  plants  are  grown  from  seed  they  often  differ 
very  markedly  from  the  parent-plant  which  produced 
the  seed.  This  variation,  whilst  a  useful  feature  when 
the  grower  is  seeking  for  new  forms  of  plants  or  striving 
to  obtain  improved  varieties,  is  one  which  is  not 
welcome  to  the  cultivator  who  sows  seed  and  wishes  to 
raise  a  crop  on  the  character  of  which  he  can  rely.  It  is 
still  more  important  in  connection  with  fruit  or  other 
trees  which  take  some  years  in  coming  to  maturity,  for 
it  is  naturally  very  disappointing  to  the  grower  to  find 


52  NATURE  TEACHING 

that  the  tree  he  has  raised  does  not  produce  fruit  of  such 
good  quality  as  the  tree  from  which  he  obtained  the 
seed,  or  that  the  ornamental  plant  obtained  has  not  the 
character  which  made  the  parent  of  value.  It  is  there- 
fore important  to  know  of  methods  by  which  plants  can 
be  propagated  and  retain  the  characters  of  the  plants 
from  which  they  are  derived.  This  is  secured  by 
planting  cuttings  and  by  budding  and  grafting :  the 
plants  raised  by  these  methods  retaining  perfectly  the 
characters  of  the  original  plants.  It  thus  follows  that 
when  a  new  and  desirable  variety  of  plant  has  been 
secured  from  amongst  the  varying  characters  exhibited 
by  seedlings,  the  cultivator  can  produce  a  large  number 
of  plants  possessing  the  desirable  characteristics  of  the 
selected  variety  by  propagating  it  by  means  of  cuttings 
or  by  grafting  or  budding. 

It  will  be  readily  understood  that  budding  and 
grafting  can  only  be  successfully  practised  with  plants 
possessing  a  cambium,  the  absence  of  a  cambium  zone 
making  these  operations  impossible  in  other  plants. 
Budding  and  grafting  are  successful  only  when  the  two 
plants  operated  upon  are  nearly  related,  thus  the  various 
varieties  of  apples  may  be  grafted  on  one  another,  and 
the  different  kinds  of  roses  grafted  on  other  roses,  but 
an  apple  cannot  be  grafted  on  a  rose,  or  a  rose  on  a 
cherry. 

Plants  possess  the  power  of  healing  up  wounds,  such 
as  are  made  when  a  branch  is  sawn  or  broken  off, 
gashes  made  in  the  stem,  etc.  The  cambium  plays  an 
important  part  in  this  process  also,  and  under  favourable 
circumstances  the  whole  wound  may  become  covered 


THE  STEM  53 

over  by  the  new  growths  which  are  formed.    Interesting 
cases  may  often  be  seen  in  wayside  trees. 

PRACTICAL  WORK 

Obtain  complete  specimens  (i.e.  with  roots,  and  if 
possible  flowers)  of  any  ordinary  non-woody  plants — e.g., 
mangolds,  grasses,  balsams,  primroses,  house-leeks,  dead- 
nettle,  etc. ;  climbing  plants,  such  as  convolvulus,  beans  ; 
creeping  plants,  such  as  creeping  jenny,  couch  grass, 
strawberry,  etc.  Notice  how  in  spite  of  all  their  differ- 
ences they  all  have  an  above-ground  "  shoot,"  made  up  of 
a  stem  (sometimes  very  short)  with  leaves  and  flowers, 
and  a  below-ground  root,  bearing  no  leaves  or  flowers. 
Make  sketches  to  illustrate  diagrammatically  the  char- 
acteristic points  of  at  least  one  example  of  each  group 
— e.g.,  a  balsam,  a  primrose,  a  bean,  and  couch  grass. 

Examine  a  leafy  shoot  of  privet,  elder,  dead-nettle, 
or  of  almost  any  other  plant  available,  and  notice  that  it 
is  made  up  of  a  stem,  bearing  leaves.  Distinguish  the 
nodes  and  internodes,  and  observe  that  the  internodes 
get  shorter  as  you  approach  the  top  of  the  stem,  the 
leaves  accordingly  becoming  more  crowded.  At  the 
very  summit  the  internodes  are  extremely  short,  and 
the  young  leaves  are  packed  together  to  form  the 
terminal  leaf-bud.  Observe  the  smaller  leaf-buds  which 
occur  just  above  the  place  where  a  leaf  joins  the  stem. 

Examine  a  privet  bush,  and  notice  that  whilst  some 
shoots  grow  upright,  others  lie  almost  horizontally,  and 
that  whilst  in  the  upright  shoots  the  leaves  are  arranged 
equally  on  all  sides  of  the  stem,  they  are  on  the  hori- 
zontal shoots  twisted  to  one  side.  Examine  closely  the 


54  NATURE  TP^ACHING 

youngest  leaves  in  both  cases,  and  observe  how  this 
apparent  great  difference  in  the  arrangement  of  the 
leaves  is  brought  about. 

Fasten  one  of  the  horizontal  shoots,  without  damaging 
it  in  any  way,  so  that  it  is  upside  down,  and  see  how  the 
young  leaves  arrange  themselves. 

Examine  also  shoots  of  hazel  nut,  ivy,  horse  chestnut, 
maple,  creeping  jenny,  and  learn  that  in  all  these  cases 
leaves  are  arranged  on  the  stems  so  that  they  may  be 
well  exposed  to  the  light,  and  do  not  shade  one  another. 
Make  drawings  of  these  leaf  arrangements. 

Uses  of  Stems. 

Dig  up  a  growing  plant  of  iris  or  flag,  wash  it  free 
from  soil,  and  notice  the  underground  stem  with  its  well- 
marked  rings.  Examine  the  youngest  part,  and  notice 
the  sheathing  bases  of  the  green  leaves.  Pull  a  leaf  off 
and  see  the  scar  it  leaves.  What  have  these  scars  to  do 
with  the  rings  seen  all  along  the  stem  ?  Look  for  leaf- 
buds  along  the  stem,  and  ascertain  how  the  stem 
branches,  and  how  new  plants  may  be  formed.  Make 
sketches  showing  all  the  parts  seen,  including  the  grow- 
ing portion,  the  leaf-scars,  the  buds,  and  the  roots. 

Examine  "  Jerusalem  "  artichokes,  noting  the  large 
number  of  slightly  projecting  scale  leaves  with  which 
they  are  covered.  If  possible,  obtain  a  whole  plant  as 
dug  up,  carefully  wash  away  the  soil,  and  see  that  the 
artichokes  are  borne  on  very  short  underground  stems 
which  are  quite  distinct  from  the  roots  of  the  plant. 

Make  drawings  of  the  whole  clump,  and  of  one 
separate  artichoke, 


THE  STEM  55 

Place  a  ripe  artichoke  to  germinate.  Notice  where 
the  new  shoots  come  from.  Notice  carefully  how,  on 
the  new  shoots,  there  is  a  gradual  transition  between 
the  scale  leaves  of  the  tuber  and  the  ordinary  green 
leaves  of  the  plant.  Draw  some  of  the  best  instances 
to  show  this. 

Dig  up  carefully  a  potato  plant,  when  the  potatoes 
are  about  half-grown,  and  wash  it  clean  from  soil  under 
a  tap.  Examine  the  underground  stems  on  which  the 
potatoes  are  borne,  looking  especially  for  any  small 
leaves  distinguishing  them  from  the  roots.  Make  draw- 
ings. Notice  the  "eyes"  in  the  potatoes.  Get  some 
seed  potatoes  and  place  them  in  damp  sand  until  they 
begin  to  sprout,  and  ascertain  whether  the  new  shoots  arise 
anywhere  on  the  potato,  or  from  the  eyes  only.  Make  a 
drawing  of  a  potato  before  it  has  started  sprouting, 
showing  the  eyes ;  and  after  it  has  sprouted,  showing  the 
young  shoots. 

Obtain  some  crocus  corrris.  Gladioli  are  still  better, 
being  larger,  but  they  are  more  expensive.  Notice  the 
dry  scale  leaves  forming  a  protective  covering,  and  the 
white  pointed  buds  at  the  top.  Pull  off  the  scale  leaves 
one  by  one,  and  compare  the  scars  they  leave  with  those 
already  seen  in  the  iris.  Cut  the  corm  through  length- 
wise ;  it  is  solid.  It  is  thus  a  stem  structure,  bearing 
leaves  (the  brown  scales)  at  definite  places  (nodes),  and 
is  in  reality  a  very  much  swollen  stem.  With  the 
help  of  a  lens,  it  is  possible  to  see  the  young  leaves  and 
the  flower,  packed  away  in  the  central  bud,  when  it  is 
cut  through.  Dig  up  crocus  plants  (i)  when  in  flower, 
and  (2)  after  the  flowers  have  died.  Make  out  where 


56  NATURE  TEACHING 

the  roots  spring  from  ;  that  the  corm  is  gradually  used 
up  and  withers  as  the  plant  flowers  and  that  a  new 
corm,  which  will  flower  next  year,  is  formed  on  top  of 
the  old  one.  Make  careful  drawings  of — (i)  a  corm  ready 
to  plant,  with  its  leaves  on ;  (2)  the  same  cut  through 
lengthwise;  (3)  the  same  with  the  leaves  stripped  off; 
(4)  a  plant  in  flower  showing  roots,  etc. ;  (5)  a  plant  after 
flowering,  showing  where  the  new  corm  arises. 

If  the  new  corm  is  always  formed  on  top  of  the  old 
one,  why  do  not  the  corms  after  a  few  years  appear 
above  the  surface  of  the  ground  ? 

Examine  plants  of  hop,  bind-weed,  and  scarlet  runner, 
thin  flexible  stems  about  any  convenient  support.  Make 
out  the  direction  in  which  the  stem  twines,  and  how  the 
free  end  of  the  stem  moves  in  a  circle  until  it  meets  with 
some  object  to  twine  around.  Make  similar  observations 
on  any  other  twining  plants  which  can  be  obtained. 

Examine  the  cucumber,  white  bryony  and  grape  vine, 
and  notice  the  special,  delicate  side  branches — tendrils 
—by  which  the  plant  clings  to  a  support.  Those  of 
the  white  bryony  and  cucumber  usually  twist  up  in  a 
beautiful  manner,  forming  a  spring,  after  they  have 
caught  hold  of  an  object,  whilst  before  this  they  stick 
straight  out.  Two  examples  only  are  mentioned  here, 
but  many  others  will  readily  be  found. 

Structure  of  Stems. 

Examine  young  and  old  pieces  of  the  stems  of  any 
of  the  following  plants  obtainable  :  elm,  horse  chestnut, 
ash,  oak,  rose,  hawthorn,  and  note,  making  careful  draw- 
ings, all  the  parts  previously  described  (p.  46).  Cut 


THE  STEM  57 

stems  both  across  and  lengthways.  Examine  the  cut 
ends  of  any  old  trees,  and  compare  with  young  plants  of 
the  same  kind,  noting  particularly  the  enormous  differ- 
ence in  thickness  of  the  wood. 

Examine  a  thick  branch  or  stem  of  a  tree  which  has 
been  cut  lengthways,  and  observe  how  the  branches,  can 
be  traced  downwards  through  the  wood  of  the  main 
branch  or  stem,  giving  rise  to  knots.  Make  drawings  of 
these  as  seen  in  both  longitudinal  and  cross  sections. 
The  trees  mentioned  above,  or  almost  any  timber  trees, 
afford  good  examples. 

Examine,  in  cross  and  longitudinal  section,  stems  of 
any  monocotyledonous  plants— for  example,  maize,  any 
large  grasses,  any  palm  (for  instance,  in  museums). 
Note  the  hard,  outer  rind,  and  the  inner,  soft,  ground- 
tissue  with  the  hard,  fibrous  strands  running  in  it.  Com- 
pare the  parts  in  these  stems  very  carefully  with  those 
of  the  dicotyledonous  stems  of  the  preceding  paragraphs. 

Grafting  and  Budding. 

To  perform  these  operations,  good,  sharp  and 
strong  knives  are  necessary.  Much  may  be  done  with 
an  ordinary  penknife,  but  proper  grafting  and  budding 
knives  greatly  facilitate  the  work.  They  are  inexpen- 
sive, and  procurable  from  any  dealer  in  gardening  tools  ; 
a  small  number  should  form  part  of  every  school's  equip- 
ment. 

Before  beginning  work  it  is  necessary  to  prepare 
supplies  of  grafting-wax  and  budding-tape.  The  follow- 
ing recipe  should  be  followed  for  preparing  grafting- 
wax  : — Melt  together  four  parts  by  weight  of  resin,  one 


58  NATURE  TEACHING 

part  of  beeswax,  and  one  part  of  tallow.  When 
thoroughly  melted,  pour  into  cold  water,  and  when  cool 
enough,  take  out  and  work  by  moulding  and  pulling 
until  it  becomes  quite  stiff.  It  is  necessary  to  have 
the  hands  well  greased  with  tallow  while  handling  this 
wax. 

Budding-tape  is  prepared  by  dipping  strips  of  cloth 
into  melted  wax.  The  wax  used  is  beeswax  mixed 
with  a  sufficient  quantity  of  kerosene  to  render  it  soft 
and  pliable,  the  mixing  being  aided  by  the  cautious 
application  of  heat ;  a  mixture  of  two  parts  of  beeswax 
with  one  of  resin  is  often  used,  the  two  substances  being 
carefully  melted  together.  Various  kinds  of  cloth  are 
employed ;  some  workers  using  linen  or  calico,  whilst 
others  prefer  thin  flannel.  The  cloth  is  torn  into  strips 
— about  |  to  f  inch  wide,  and  of  convenient  length — 
which  are  dipped  into  the  melted  wax,  then  lifted  out, 
and  all  the  superfluous  wax  allowed  to  drain  off;  when 
cool  the  strips  are  ready  for  use.  A  sufficient  supply  of 
budding-tape  to  last  for  some  time  should  be  prepared. 

Some  of  the  forms  of  adhesive  plaster,  as  used  by 
surgeons,  which  can  be  purchased  from  druggists  in 
narrow  widths  (J  to  f  inch)  on  reels,  may  be  usefully 
and  conveniently  substituted  for  budding-tape. 

Grafting  by  approach : — Select  two  trees  of  the 
same  kind  but  presenting  some  points  of  difference,  as 
two  apples,  two  roses,  or  two  currants ;  one  or  both  of 
the  selected  trees  should  be  growing  in  a  pot  or  tub,  so 
that  the  two  trees  may  be  brought  together.  Now  decide 
which  tree  is  to  form  the  stock  and  which  is  to  provide 
the  scion.  Select  a  branch  of  each — conveniently  situ- 


THE  STEM  59 

ated,  so  that  the  two  branches  can  be  brought  into  close 
contact — taking  care  that  the  selected  branches  are  of 
nearly  the  same  thickness  at  the  points  where  they  are 
to  be  operated  upon.  Devise  some  means  whereby  the 
two  plants,  or  at  least  the  two  selected  branches,  may 
be  firmly  secured,  so  that  the  scion  may  be  kept  in 
position  on  the  stock.  The  method  of  doing  this  will 
depend  on  the  size  and  character  of  the  two  plants ; 
merely  binding  the  two  branches  together  will  be 
sufficient  in  many  cases,  or,  if  the  stock  is  a  large  tree 
and  the  plant  providing  the  scion  is  contained  in  a  pot, 
the  latter  can  be  secured  to  the  trunk  or  to  a  branch  of 
the  stock.  Having  made  these  preparations,  cut  away 
a  piece  of  the  stock  at  the  selected  point,  removing 
from  two  to  four  inches  of  the  bark  with  a  little  of  the 
wood  below  it,  taking  care  that  the  cut  is  smooth  and 
even.  Make  a  similar  cut  on  the  scion,  in  such  a 
position  that  the  two  cut  surfaces  may  be  brought  into 
close  contact  and  will  fit  together  fairly  well.  Bring  the 
two  surfaces  together,  secure  them  in  position  by  means 
of  strong,  soft  twine  tied  both  above  and  below  the 
place  operated  upon,  and,  finally,  wrap  a  strip  of  bud- 
ding-tape firmly  around  the  united  branches  covering 
the  junction  completely ;  the  edges  of  the  tape  should 
overlap,  so  as  to  prevent  the  evaporation  of  moisture 
from  the  cut  surfaces,  or  the  access  of  rain-water  to  the 
joint.  It  is  not  necessary  to  tie  the  budding-tape,  for 
the  end  will  remain  in  place  if  pressed  down  on  the 
surface  of  the  tape  bandage,  the  wax  holding  it  securely. 
Everything  being  properly  and  securely  fixed,  leave  the 
plants  for  a  sufficient  time  for  union  to  take  place  and 


60 


NATURE  TEACHING 


then  cut  off  the  scion  below  the  place  of  grafting,  and 
trim  the  cut  end  neatly  with  a  sharp  knife. 

Grafting  stems  of  equal  size : — In  this  method  we 
employ  as  before  a  rooted  plant  as  the  stock,  but 
only  a  detached  portion  of  the  plant  we  desire  to  graft 
on  to  it  as  the  scion.  Cut  back  the  stock  to  a  place 
where  its  stem  is  of  about  the  same  thickness  as  the 
scion.  Shape  the  cut  ends  of  stock  and  scion,  so  that 


FlG.  5. — Showing  modes  of  shaping  the  cut  ends  of  stock  and 
scion  when  grafting  stems  of  equal  size. 

they  may  fit  together  accurately,  with  their  cambial 
regions  in  contact.  As  soon  as  scion  and  stock  are  thus 
fitted  together,  secure  them  in  position  by  firmly  bind- 
ing with  binding-tape,  taking  great  care  that  they  are 
so  securely  fixed  that  no  displacement  can  take  place, 
and  that  the  joint  is  so  well  covered  that  the  cut 
surfaces  will  not  dry. 

This  method  admits  of  several  variations  in  the 
manner  of  shaping  the  cut  ends  of  stock  and  scion  (see 
Fig.  5).  In  the  simplest  case,  cut  the  two  ends  obliquely 


THE  STEM 


61 


and  merely  place  them  in  position  ;  the  disadvantage  of 
this  method  is  that  they  are  very  liable  to  slip.  Means 
must  be  taken,  therefore,  to  prevent  this,  and  it  is  usual 
to  cut  a  notch  in  the  end  of  the  stock  and  a  correspond- 
ing tongue  or  projection  at  the  end  of  the  scion  ;  or  the 
end  of  the  stock  may  be  trimmed  to  a  wedge,  and  in  the 
scion  a  Y-shaped  incision  made  to  fit  accurately  over 
the  wedge.  The  form  of  the  joint  adopted  may  be 
varied  indefinitely,  but  the  great  object  to  be  kept 
steadily  in  view  is  the  bringing  of  the  cambial  regions 
of  the  two  cut  surfaces  into  close  contact  and  retaining 
them  there. 

Grafting  a  small  scion  on  to  a  large  stock : — In  this 
case,  as  the  cambium  only  forms  a  narrow  ring  near 
the  outer  margin  of  the  stock, 
it  is  essential  that  the  scion 
be  placed  here  also.  The 
simplest  method  of  working 
is  as  follows  : — Trim  the  end 
of  the  scion  to  a  long  wedge 
and  thrust  this  wedge  into 
the  cambium  of  the  stock, 
that  is,  between  its  wood  and 
bark.  Another  method  is  to 
cut  a  V-snaPed  piece  of  bark  ,-,  ,  cu  . 

v  FlG.    6. — Showing 

til 


grafting  a  small 
large  stock. 


a    method    of 
scion  on  to  a 


from  the  stock,  carrying  the 
incision  deep  enough  to  re- 
move a  portion  of  the  wood  also  (see  Fig.  6).  Then  cut 
the  end  of  the  scion  to  a  corresponding  shape  and  fit  it 
into  the  stock,  and,  having  taken  care  to  leave  the  bark 
undisturbed  on  one  side  of  the  scion,  bring  it  into  posi- 


62  NATURE  TEACHING 

tion  so  that  it  fits  on  to  the  bark  of  the  stock.  Fix  the 
scion  in  place  by  means  of  grafting-wax,  so  moulding 
and  pressing  it  around  the  joints  and  cut  surfaces  as  to 
fulfil  the  double  purpose  of  holding  the  scion  in  position 
and  protecting  it  from  drying  up.  This  mode  of  graft- 
ing is  adopted  when  it  is  desired  to  graft  on  to  a  thick 
branch  or  the  stem  of  a  tree  which  has  had  all  its 
branches  removed ;  several  scions  may  be  put  on  one 
stock. 

Apple,  pear,  apricot,  or  other  fruit  trees  available,  are 
suggested  for  grafting  experiments. 

Budding: — For  practice  the  pupil  should  work  upon 
rose  plants.  Examine  the  tree  which  is  to  furnish  the 
bud-wood,  cut  off  two  or  three  vigorous  branches  with 
well-developed  side  leaf-buds,  and  carry  these  to  the 
tree  which  is  to  be  the  stock.  Select  a  place  on  a  young 
but  fairly  woody  branch  of  the  stock,  and  make  a  "]~- 
shaped  incision  in  the  bark,  with  the  downward  cut  about 
an  inch  and  the  cross  cut  about  three-quarters  of  an  inch 
in  length  (see  Fig.  7).  Raise  the  bark  gently  from  the 
wood,  taking  care  not  to  tear  it  from  the  branch — the 
flattened  end  of  the  budding  knife  should  be  used  for  this 
purpose.  The  stock  being  now  prepared,  choose  a  good 
bud  on  the  branches  already  selected,  and  cut  off  the  leaf 
which  accompanies  it,  leaving  only  a  very  short  piece  of 
the  leaf-stalk ;  then  with  a  firm  clean  cut  remove  the  bud, 
together  with  a  thin  slice  of  the  wood  beneath.  The 
whole  piece  so  removed,  including  bud,  bark,  and  wood, 
should  be  about  three-quarters  of  an  inch  long  and  one 
quarter  wide.  Insert  the  bud  thus  prepared  under  the 
bark  of  the  stock,  proceeding  carefully  so  as  not  to  tear 


THE  STEM 


63 


or  unnecessarily  injure  the  bark.     All  these  operations 

should  be  performed  as  quickly  as  possible,  to  avoid  the 

drying  up  of  the  cut  surfaces.     As  soon  as  the  bud  is  in 

position  fix  it  by  one  or  two  turns  of  thin,  soft  twine  or 

other  material,  then  take  a  strip  of  budding -tape  and 

wrap  round  the  stock  with  the 

inserted  bud,  beginning  slightly 

below   the    place    of    operation 

and  allowing  the  edges  of  the 

tape   to   overlap   at   each   turn. 

The  bud  may  be  covered  over 

completely,  or,  if  very  prominent, 

it   may   be    left    exposed ;    the 

budding-tape  should  hot  be  tied, 

the  free  end  being  held  safely  in 

position  by  pressing  it  down  on 

the  wrapped  portion. 

Budding     is    frequently    re- 
sorted to  in  tropical  countries,  FIG.  7.-£u<timg.-The  upper 


right-hand  figure  shows  the 
bud  ready  for  insertion  under 
the  cut  bark  of  the  stock 
(upper  left-hand).  The 
lower  left-hand  figure  shows 


the  bud  in  position,  aud  the 
remaining  figure  illustrates 
it  bound  up  in  the  budding 
tape. 


with  oranges,  lemons  and  other 
citrus  fruits,  when  it  is  desired 
to  grow  some  selected,  choice 
kind  upon  a  stock  of  a  hardy 
variety.  For  this  purpose  seed- 
lings of  the  kind  to  be  used  for 
the  stocks — in  practice  often  sour  oranges  or  "  rough  " 
lemons — should  be  raised  in  nursery  beds.  When  the 
stems  are  of  about  the  thickness  of  one's  finger,  insert 
buds  of  the  selected  variety  in  the  stem  of  the  stock, 
three  or  four  inches  above  the  level  of  the  ground.  In 
about  ten  to  fourteen  days  the  buds  should  be  found  to 


64  NATURE  TEACHING 

be  securely  united  to  the  stocks,  when  the  wrappings 
of  budding-tape  may  be  removed.  Four  or  five  days 
after  this,  cut  part-way  through  the  stem  of  the  stock, 
about  an  inch  or  two  above  the  inserted  bud,  and 
bend  down  the  top  of  the  stem  from  the  cut  point, 
so  as  to  lie  along  the  surface  of  the  ground.  The 
flow  of  sap  to  the  upper  part  of  the  stock  is  thus 
checked,  and  increased  growth  of  the  bud  results. 
When  each  bud  has  developed  into  a  good  strong 
branch,  cut  off  the  now  prostrate  stem,  and  trim  down 
the  stump  close  to  the  point  where  the  branch  aris- 
ing from  the  bud  grows  out,  so  that  the  scar  may 
heal  neatly,  and  the  new  branch  may  grow  straight  as  a 
continuation  of  the  stem,  and  thus  form  a  shapely  tree. 
Should  any  bud  develop  at  any  point  below  the  place 
where  budding  took  place,  it  must  be  rubbed  or  pinched 
off. 

To  ensure  success  in  budding,  the  work  must  be  done 
when  the  stock  is  in  such  a  condition  that  the  bark  can  be 
easily  raised,  this  occurring  when  the  cambium  is  in  a 
state  of  active  growth.  Skill  is  also  necessary  in  selecting 
good  bud-wood  from  which  to  cut  the  buds.  The  work 
should  be  practised  regularly,  until  each  pupil  can  work 
rapidly,  neatly,  and  with  a  small  percentage  of  failures. 
This  branch  of  work  should  not  be  dismissed  in  a  lesson 
or  two,  but  real  practical  skill  should  be  acquired  by 
repeated  exercise. 

Healing  of  Wounds. 

Examine  these  places  on  trees  where  branches  have 
been  cut  off  or  broken  off,  and  notice  how,  after  a  time,  new 


THE  STEM  65 

growths  have  formed  whereby  the  wounds  are  healed. 
This  healing  of  wounds  is  of  great  importance  to  the  plant, 
as,  just  as  in  animals,  an  open  wound  is  often  the  cause 
of  the  plant  developing  some  disease.  All  cases  seen 
should  be  examined  carefully,  and  accurate  drawings 
made. 


CHAPTER  IV 

THE   LEAF 

DURING  the  previous  practical  work  we  have  had 
occasion  to  observe  the  structures,  known  as  leaves, 
which  are  borne  on  the  stems  of  plants.  It  is  a  matter 
of  common  knowledge  that  the  leaves  of  different  plants 
vary  greatly  in  size,  character  and  shape,and  we  commonly 
distinguish  plants,  when  not  in  flower,  by  the  shape  of 
their  leaves.  Apart  from  these  minor  differences  many 
leaves  agree  in  having  a  more  or  less  thin,  flattened, 
green  portion,  known  as  the  blade  of  the  leaf,  which  may 
be  "  simple  "  in  shape,  as  a  privet,  elm,  or  nasturtium  leaf, 
or  much  divided,  as  an  ash,  rose,  or  vetch  leaf.  In  many 
plants — for  example,  the  sow-thistle  or  honeysuckle — this 
leaf-blade  joins  directly  on  to  the  stem,  but  in  others  it 
has  a  thinner,  generally  rounded,  lower  portion,  the  leaf- 
stalk, easily  seen  in  a  maple,  horse  chestnut  or  nasturtium. 
In  addition  to  these  two  parts  many,  but  by  no  means 
all,  leaves  show,  at  the  point  where  they  join  the  stem,  a 
pair  of  bodies  which  are  known  as  stipules.  These  may 
be  small,  as  in  the  garden  geranium,  or  comparatively 
large,  as  in  the  pea,  pansy  and  hawthorn. 

The  blade  of  the  leaf  has  been  spoken  of  hitherto  as 


THE  LEAF  67 

a  thin  expansion.  This  is  true  in  by  far  the  greater 
number  of  plants,  but  many  plants,  especially  those  which 
live  in  very  dry  places  or  near  the  sea,  have  leaves  which 
are  either  thick  and  fleshy,  as  in  the  house-leek,  or  very 
small,  as  in  the  heather  and  furze.  We  have  also  seen 
already,  when  examining  iris,  artichoke  and  crocus  stems, 
that  leaves  are  not  always  green.  Other  examples  of  the 
various  characters  which  leaves  can  assume  will  be  met 

with  later. 

Uses  of  Leaves. 

Leaves  are  necessary  for  the  health  and  growth  of 
most  plants,  as  in  them  are  carried  on  the  processes  of 
breathing  and  the  manufacture  of  food-material.  The 
consideration  of  these  processes  is,  however,  best  deferred 
until  we  have  made  ourselves  acquainted  with  the  struc- 
ture of  leaves.  We  will  therefore  first  deal  with  their 
other  less  important  uses. 

The  young  leaves  of  most  plants  are  very  delicate 
and  easily  damaged  by  exposure  to  the  sun,  wind,  and 
frost.  It  is  common  to  find  these  young  leaves  protected 
by  being  enclosed  by  the  older  ones,  as  may  be  seen  in 
the  leaf-buds  of  the  lilac  and  privet,  and  very  strikingly 
in  cabbages  and  lettuces.  In  the  docks  the  young  leaves 
are  rolled  up  within  the  next  older  leaf,  and  specially 
protected  from  drying  up  by  being  bathed  in  a  sticky 
liquid.  The  school  garden  will  readily  furnish  numerous 
other  interesting  cases.  In  the  common  red  clover  the 
stipules  protect  the  young  leaves.  In  many  plants — for 
instance,  the  pear,  apple,  and  beech — the  stipules  are 
small,  and  look  at  first  sight  mere  useless  structures. 
Examination  of  the  buds  of  these  plants  shows  that  this 


68  NATURE  TEACHING 

is  the  time  when  the  stipules  are  of  use,  as  then  they  are 
large  in  comparison  with  the  young  leaves  and  serve  to 
cover  and  protect  them. 

We  have  so  far  confined  our  attention  to  the  buds 
found  during  the  warm  season  of  the  year,  when  the 
plants  are  actively  growing,  and  all  that  is  necessary  is 
to  protect  the  delicate  young  leaves  from  the  wind  and 
sun,  and  possibly  from  cold  during  the  night.  In  some 
parts  of  the  world  it  is  "always  summer,"  the  plants 
there  are  almost  continually  growing,  and  we  find  buds 
of  this  nature  the  whole  year  through.  In  Great  Britain 
and  other  temperate  countries,  the  conditions  are  very 
different,  and  summer  and  winter  follow  each  other 
regularly.  We  are  all  familiar  with  the  sight  of  trees 
and  other  plants  growing  through  the  summer,  ceasing 
to  grow  in  the  autumn,  and  as  soon  as  the  weather  begins 
to  turn  cold  dropping  their  leaves  and  becoming  quite 
bare.  In  this  condition  they  remain  during  the  winter, 
to  all  appearance  dead,  but  they  are  only  resting,  and  as 
soon  as  the  weather  turns  warm  again  young  leaves 
reappear  and  the  plants  once  more  enter  on  their 
growing  stage.  The  bursting  into  leaf  of  trees  and 
shrubs  is  one  of  the  most  constant  features  of  the  spring 
in  temperate  climates. 

If  we  examine  trees — for  instance,  a  horse  chestnut 
— during  the  winter  we  find  no  leaves,  but  a  number  of 
large  brown  bodies — the  buds — covered  with  more  or  less 
sticky  scales.  One  of  these  buds  carefully  pulled  to 
pieces  will  be  found  to  be  covered  on  the  outside  by  a 
series  of  overlapping  brown  scales,  and  to  contain  inside 
a  number  of  small  green  leaves  well  wrapped  up  in  what 


THE  LEAF  69 

looks  almost  like  cotton-wool.  It  is  in  fact  an  ideal 
arrangement  for  protecting  the  young  leaves  from  the 
cold  and  wet.  The  cotton-wool-like  material  keeps  the 
leaves  warm,  and  the  overlapping  scales,  fastened  to- 
gether by  the  sticky  liquid,  make  a  waterproof  covering. 

On  a  warm  day  in  early  spring  the  sticky  material 
melts,  and  the  buds  glisten  in  the  sunshine.  If  the  warm 
weather  continues,  the  scales  are  thrust  apart  and  the 
tender  green  leaves  come  out  and  give  the  well-known 
green  flush  of  spring  to  the  whole  tree. 

How  real  the  protection  the  buds  afford  to  the 
young  leaves  and  flowers  is  well  shown  by  the  great 
damage  done,  if  a  spell  of  warm  weather  sufficient  to 
make  some  of  the  buds  open  is  followed  by  frosts. 
It  is  the  opened  buds  then  which  suffer;  those  which 
remained  closed  being  quite  uninjured  by  the  frost 

We  have  already  seen  in  the  iris  and  crocus  the  dry 
scale  leaves  wrapping  over  the  underground  buds,  and 
that  when  these  buds  grow  into  leafy  shoots  these  scale 
leaves  wither  away.  In  other  plants  underground  leaves 
are  found,  which  act  as  storehouses  of  food.  The  common 
garden  lilies,  such  as  the  tiger  and  white  lilies,  or  an 
onion,  serve  as  good  examples;  and  on  digging  up  one 
of  their  bulbs  with  the  above-ground  leaves  still  attached, 
it  will  be  readily  seen  that  the  thick,  fleshy  structures 
which  make  up  the  greater  part  of  the  bulb,  are  really 
only  the  thickened  bases  of  leaves,  and  are  of  use  to 
contain  starch  and  other  food-reserves.  That  is  to  say, 
we  find  leaves  in  these  plants  performing  exactly  the 
same  duties  which  the  stem  does  in  the  iris,  crocus,  and 
potato,  and  the  root  in  the  radish,  turnip  and  beet 


70  NATURE  TEACHING 

Leaves  often  act  as  the  climbing  organs  of  the  plant, 
and  all  gradations  can  readily  be  found  between  an 
ordinary  green  leaf  which  has  the  power  to  hold  on  to, 
or  even  twist  round  supports  and  the  special  structures 
of  other  plants,  often  so  much  altered  to  make  them 
more  suitable  for  this  particular  use  that  they  have 
almost  lost  their  leafy  character.  Thus  in  the  wild 
clematis  (traveller's-joy  or  old  man's  beard)  so  common 
on  chalk  and  limestone  districts,  the  leaf-stalk  twists 
round  objects  and  holds  the  plant  up ;  similarly  in  the 
garden  nasturtium  the  leaf-stalks  of  the  ordinary  green 
leaves  do  the  same.  In  the  garden  pea  only  a  special  part 
of  the  leaf — the  long  thin  end — is  of  use  as  a  climbing 
organ,  and  similarly  in  many  of  the  vetches.  Examples 
like  these  are  of  special  interest,  as  they  show  us  how 
adaptable  the  parts  of  plants  are,  and  how  the  same  part 
can  serve  very  different  purposes. 

Structure  of  Leaves. 

In  most  leaves  the  blade  has  running  through  it  a 
number  of  veins,  often  conspicuous,  especially  on  the 
lower  side,  as  ridges.  The  leaves  of  the  maple,  black- 
berry, and  indeed  almost  any  ordinary  thin  leaves,  show 
them  very  plainly,  and,  on  holding  such  leaves  to  the 
light,  it  is  seen  that  there  is  a  perfect  network  of  these 
veins,  the  small  veins  being  branches  of  the  larger  ones. 
These  veins  are  really  the  continuations  of  the  woody 
tissue  which  we  have  already  seen  in  the  stem,  and  are 
of  use  as  a  supporting  framework  to  the  soft  tissue  of 
the  leaf,  spreading  it  out  to  the  light  and  air,  and  pre- 
venting the  leaf  from  being  readily  torn.  They  are  also 


THE  LEAF  71 

the  means  whereby  the  water  taken  up  by  the  roots  is 
brought  to  the  leaf,  and  the  substances  manufactured  in 
the  leaf  are  carried  away  to  the  other  parts  of  the  plant. 

The  veins  of  leaves  are  arranged  in  two  main  ways ; 
netted,  as  in  the  examples  above  ;  parallel,  as  in  the  lily, 
wheat,  barley,  and  all  grasses  where  the  veins  run  side 
by  side  and  do  not  form  an  interlacing  network.  These" 
two  types  of  vein  arrangement — netted  and  parallel — 
are,  on  the  whole,  characteristic  of  the  leaves  of  dicoty- 
ledons and  monocotyledons  respectively,  and  with  certain 
exceptions; — for  instarice,  the  black  bryonyr^-may  be 
taken  as  indicating  to  which  of  these  two  groups  a  plant 
belongs. 

It  is  impossible,  without' the  use  of  a  microscope,  to 
obtain  very  much  information  concerning  the  internal 
structure  of  leaves.  If,  however,  we  select  some  thicks 
leaved  plant,  such  as  the  iris,  we  find  that  both  upper  and 
lower  surfaces  of  a  leaf  are  covered  with  a  colourless  skin, 
which,  with  a  little  care,  can  be  stripped  off*.  The  main 
mass  of  the  leaf  is  seen  to  be  made  up  of  comparatively 
soft  tissue,  through  which  harder,  fibrous  strands  (the 
veins)  run.  The  thin  skin  makes  a  kind  of  waterproof 
coating  to  the  leaves,  but  has  an  enormous  number  of 
minute  openings,  called  stomata  (too  small  to  be  seen 
without  a  magnifying  glass),  through  which  the  gases  of 
the  atmosphere  can  pass  in  and  out,  and  so  reach  the 
spongy  tissue  of  the  inside  of  the  leaf.  This  is  most 
important,  for  it  is  in  this  inner  part  that  the  real  work 
of  the  leaf,  the  breathing  and  building  up  of  new  matter, 
goes  on,  and  for  these  processes  a  free  interchange  of 
gases  with  the  outside  air  is  absolutely  necessary. 


72  NATURE  TEACHING 

Transpiration. 

Everyday  experience  shows  us  that  if  a  leafy  shoot 
is  picked  it  soon  becomes  limp  and  then  withers,  but 
that  if  we  place  it  in  water  it  remains  fresh  and  stiff  for 
a  longer  time.  Further,  we  know  that  a  shoot  which 
has  commenced  to  wither  can  often  be  made  fresh 
again  by  placing  the  cut  end  of  its  stalk  in  water. 
Similarly,  plants  growing  in  the  ground  droop  and  may 
die  if  they  are  deprived  of  water  for  a  long  time.  They 
soon  revive  if  water  is  poured  on  the  soil  so  as  to 
penetrate  down  to  their  roots.  From  these  various 
facts  it  is  clear  that  the  withering  and  limpness  of  the 
leaves  is  due  to  the  fact  that  they  give  off  water,  and 
that  more  can  be  supplied  to  them  either  by  putting 
the  cut  end  of  the  stalk  in  water,  or,  as  happens  in 
nature,  by  water  being  taken  up  by  the  roots  and 
passed  on  through  the  stem  to  the  leaves. 

This  loss  of  water  by  the  leaves  is  known  as  tran- 
spiration^  and  is  of  great  importance  to  the  plant, 
because  as  water  is  given  off  from  the  leaves  more  is 
steadily  drawn  up  through  the  stem  to  take  its  place. 
When  a  plant  is  growing  and  has  plenty  of  water  at  its 
roots,  water  is  taken  up  almost  as  quickly  as  it  is  given 
off,  and  the  whole  plant  remains  fresh  ;  but  if  there  is 
none  or  only  very  little  water  to  be  obtained,  as  in  the 
cut  shoot  or  the  plant  in  dry  ground,  the  roots  cannot 
take  up  enough  to  make  up  for  what  the  leaves  give  off, 
and  first  the  leaves  and  afterwards  other  parts  of  the 
plant  droop  and  wither. 

In  transpiration,  the  green  spongy  tissue  of  the  leaf 


THE  LEAF  73 

gives  off  moisture  which  escapes  into  the  outside  air 
through  the  minute  openings  in  the  surfaces  of  the  leaf. 
These  openings  are  able  to  open  and  close  according  to 
conditions,  and  so  regulate  the  rate  at  which  water  can 
be  given  off.  When  the  air  is  dry  they  become  smaller, 
and  so  hinder  the  escape  of  water.  We  shall  see,  too, 
from  our  practical  work  that  light  has  an  important 
effect,  and  that  plants  give  off  more  water  when  exposed 
to  the  light  than  when  in  the  shade.  When  cuttings  of 
plants  are  being  taken  the  shoots  are  separated  from 
their  roots  and  cannot  obtain  much  water.  It  will  be 
clear  now  why,  under  such  circumstances,  some  of  the 
leaves  should  be  cut  off  and  the  cuttings  placed  in  the 
shade* 

We  can  easily  measure  how  much  water  a  single 
leaf  or  a  whole  plant  gives  out  during  a  certain  time, 
and  experiments  for  doing  so  are  described  in  the 
practical  work  on  this  chapter. 

Another  point  of  interest  is  to  find  out  whether  this 
water  is  given  off  equally  from  the  upper  and  lower 
surfaces  of  the  leaf,  or  more  from  one  surface  than  the 
other.  An  experiment  to  enable  this  to  be  ascertained 
is  also  described. 

In  a  long  drought  there  is  often  insufficient  water  to 
counterbalance  that  given  off  by  the  leaves,  and, 
although  the  pores  may  be  closed,  there  is  danger  of 
injury  to  the  plant  from  excessive  loss  of  water.  To 
prevent  this,  some  leaves — for  instance,  of  many  grasses, 
and  particularly  those  which  grow  in  dry,  sandy  places — 
have  the  power  of  curling  themselves  up  so  as  to  cover 
the  pores  (stomata)  with  the  over-arched  leaf-blade, 


74  NATURE  TEACHING 

thus  further  reducing  evaporation.  Many  leaves  have 
their  pores  so  placed  that  when  the  leaf  is  curled  up 
during  dry  weather  they  are  all  under  cover,  none 
being  present  on  the  exposed  outer  side.  Thus  it  will 
be  seen  that  order  prevails  even  under  such  disturbing 
conditions  as  those  which  lead  to  the  withering  of 
leaves  by  drought,  when  all  appears  confusion.  There 
are  many  other  contrivances  for  protecting  plants  from 
excessive  loss  of  water.  Amongst  the  most  common 
are  the  thickening  of  the  outer  skin,  well  seen  in  house- 
leek,  laurels,  box,  etc.,  the  provision  of  a  coating  of  hair, 
for  instance,  in  the  mullein,  and  by  the  reduction  in  size 
of  the  leaves,  as,  for  example,  in  the  pines,  heaths,  furze, 
and  other  plants  which  can  live  in  situations  where  they 
get  but  little  moisture. 

It  is  important  that  the  pores  in  the  leaf  should  be 
enabled  to  perform  their  functions  under  all  the 
conditions  to  which  the  plant  may  be  exposed."  We 
have  already  seen  how  in  some  plants  they  are  covered 
and  protected  during  drought.  It  is  also  often  essential 
that  they  should  not  be  readily  filled  by  drops  of  water 
during  rain  or  dew,  and  the  surfaces  of  leaves  often 
have  slightly  waxy  or  hairy  coatings,  so  arranged  that 
those  parts  of  the  leaf  which  are  abundantly  provided 
with  pores  are  extremely  difficult  to  wet,  while  surfaces 
with  few  pores  are  wetted  easily.  Good  instances  of 
this  are  seen  in  leaves  which  are  easily  wetted  on  the 
upper  surface  where  there  are  no  pores,  but  which 
throw  off  water  from  their  under  surfaces  in  a  wonderful 
manner.  The  leaves  of  water-lilies,  duck-weed,  frog- 
bit,  etc.,  cannot  be  wetted  on  their  upper  surfaces, 


THE  LEAF  75 

but  the  under  surfaces  live  in  constant  contact  with 
water. 

It  is  interesting  to  observe  how  the  leaves  of  plants, 
by  their  position  and  arrangement,  throw  in  different 
directions  the  water  which  falls  on  them  as  rain.  In 
many  plants,  as,  for  example,  beet,  violet,  dandelion,  the 
leaves  are  so  arranged  that  much  of  the  water  which 
falls  on  them  is  directed  towards  the  centre  of  the  plant, 
moistening  the  ground  near  its  base,  where  the  main 
roots  are  to  be  found.  As  the  plant  grows,  the  leaves 
often  bend  downwards  at  the  tops  while  still  inclined 
inwards  at  the  base.  There  is  thus  a  division  of  the 
rain,  a  portion  flowing  towards  the  stem,  and  a  portion 
towards  the  outer  boundary  of  the  plant,  a  greater  area 
of  soil  being  thus  moistened.  This  may  be  observed  in 
the  sunflower.  In  many  large  trees,  amongst  other 
plants,  practically  all  the  water  is  thrown  away  from 
the  trunk,  so  that  there  is  a  dry  space  beneath  the 
leaves  and  branches ;  water  is  not  wanted  there,  for 
there  are  no  young  roots  to  absorb  it  near  the  trunks  of 
such  plants.  Close  observation  has  revealed  a  relation- 
ship between  the  direction  and  spread  of  the  rootlets 
and  the  drainage  system  of  the  leaves  of  a  plant.  In 
those  plants  with  widely-spreading  roots  the  water  is 
conducted  towards  the  margin  of  the  plant  system  (oak 
and  many  other  trees).  In  those  with  bulbous  roots,  or 
with  closely-tufted  rootlets,  or  with  deep,  penetrating 
taproots,  the  water  is  commonly  conducted  towards  the 
centre  (violets,  beet,  lilies). 

A  plant  breathes,  just  as  animals  do,  and  also 
obtains  a  large  proportion  of  its  food  from  the  air 


76  NATURE  TEACHING 

through  the  agency  of  its  leaves.  In  order,  however,  to 
understand  the  various  processes  which  go  on  in  the 
leaf,  it  is  necessary  to  know  something  concerning  the 
composition  of  the  atmosphere. 

TJte  Atmosphere. 

The  atmosphere  consists  almost  entirely  of  two  gases, 
oxygen  and  nitrogen,  which  relatively  compose  one-fifth 
and  four-fifths  of  its  volume.  Oxygen  is  the  substance 
by  whose  agency  all  burning  or  combustion  takes  place, 
and  which,  in  the  breathing  of  animals,  removes  the 
waste  products  from  the  blood  by  a  process  of  slow 
combustion.  Nitrogen,  on  the  other  hand,  is  an  inactive 
gas  which  serves  to  dilute  the  oxygen  and  modify 
the  rapidity  and  vigour  of  its  action.  In  addition  to 
these  two  gases  there  are  present  very  small  quantities 
of  water-vapour  and  carbonic  acid  gas  or  carbon  dioxide 
— so  called  because  it  is  formed  by  the  union  of  the  two 
substances  carbon  and  oxygen. 

Carbon  exists  in  various  forms,  the  commonest  being 
ordinary  charcoal,  which  is  very  nearly  pure  carbon.  All 
organic  substances — that  is,  all  substances  which  are  the 
product  of  life,  become  blackened  or  charred  when 
strongly  heated.  This  charring  may  be  taken  as  proof 
of  the  presence  in  them  of  carbon.  We  thus  recognise 
the  truth  of  the  assertion  that  all  organic  matter  contains 
carbon.  If,  however,  the  heating  is  continued  still 
further,  the  oxygen  of  the  air  unites  with  the  carbon, 
forming  the  gas  carbon  dioxide,  and  the  substance  has 
then,  we  usually  say,  "  burnt  away." 

The  presence  of  carbon  dioxide  can  readily  be  made 


THE  LEAF  77 

visible  by  taking  advantage  of  the  property  which  it 
possesses  of  combining  with  lime  to  form  chalk.  If  a 
solution  of  lime  in  water — that  is,  clear  lime-water — is 
brought  into  contact  with  carbon  dioxide,  chalk  is  formed, 
and,  being  insoluble  in  water,  becomes  at  once  apparent 
by  the  milky  or  turbid  appearance  it  gives  to  the 
water. 

Plants  and  the  Atmosphere. 

On  breathing  into  lime-water  it  soon  becomes 
cloudy,  owing  to  the  carbon  dioxide  present  in  our 
breath.  Plants  can  easily  be  shown  to  produce  a  similar 
effect.  We  see,  therefore,  that  both  animals  and  plants 
breathe  out  carbon  dioxide,  and,  as  it  is  also  formed  in 
the  burning  of  wood,  coal,  and  all  other  substances  con- 
taining carbon,  it  follows  that  carbon  dioxide  is  con- 
tinually being  added  to  the  air  in  large  quantities.  But 
carbon  dioxide,  when  present  to  a  certain  degree,  is 
injurious  to  life,  and  yet  for  countless  ages  the  actual 
amount  of  carbon  dioxide  in  the  atmosphere  has  not 
increased.  It  follows,  therefore,  that  there  must  be  some 
agency  at  work  whereby  its  accumulation  in  the  air  is 
prevented,  or  all  life  would  become  impossible.  Plants 
are  the  means  whereby  this  accumulation  is  hindered. 
When  carbon  dioxide  comes  in  contact  with  the  living 
substance  of  the  plant,  under  certain  conditions,  it  is 
split  up  into  its  constituent  parts,  carbon  and  oxygen. 
The  carbon  is  kept  by  the  plant  and  built  up  into  its 
tissues,  and  the  oxygen  set  free.  The  conditions  referred 
to  above  are  the  presence  of  (i)  the  green  colouring 
matter  (leaf-green  or  chlorophyll)  which  gives  the 


78  NATURE  TEACHING 

characteristic  colour  to  the  leaves,*  and  in  some  cases 
the  stems  of  plants,  and  (2)  sunlight. 

The  process  which  goes  on  in  the  leaf  whereby  the 
carbon  dioxide  is  broken  up  in  this  way  and  the  carbon 
used  by  the  plant  is  known  as  assimilation.  Assimilation 
must  be  very  carefully  distinguished  from  the  respiration 
or  breathing  of  plants,  in  which,  exactly  as  in  that  of  all 
animals,  oxygen  is  taken  in  and  carbon  dioxide  given 
out.  A  plant  is  always  breathing,  but  can  only  carry  on 
the  process  of  assimilation  under  the  special  conditions 
mentioned  above.  Whilst  a  plant  is  in  the  sunlight  the 
oxygen  given  out  masks  the  breathing  process,  and  it  is 
only  when  plants  are  in  darkness,  either  artificial  or  that 
ordinarily  occurring  at  night,  that  the  fact  that  a  plant 
does  really  breathe  out  carbon  dioxide  like  an  animal 
can  be  detected.  When  later  we  try  experiments  on  the 
breathing  of  plants,  it  is  essential  to  remember  that  the 
plants  must  be  kept  in  the  dark. 

The  Food  of  Plants. 

As  the  result  of  the  building-up  processes  which  go 
on  in  the  leaf,  we  find  that  starch  is  formed.  In  the 
practkal  work  at  the  end  of  this  chapter,  experiments 
are  described  which  enable  us  to  prove  (i)  that  starch  is 
actually  formed  in  leaves ;  (2)  that  for  this  formation  of 
starch,  by  the  living  substance  of  the  plant,  leaf-green 
and  sunlight  and  the  presence  of  carbon  dioxide  are 
necessary  conditions. 

*  In  some  plants — for  instance,  copper  beech,  coleus — the  colour 
of  the  leaf-green  is  hidden  by  other  colours.  But  the  leaf-green  is 
always  there  nevertheless. 


THE  LEAF  79 

Starch  is  a  very  common  substance  in  plant  tissues. 
It  is  one  of  the  chief  forms  in  which  plants  store  up 
reserves  of  food  to  be  used  on  some  future  occasion, 
when  greater  demands  are  made  for  food  than  can  be 
supplied  by  the  assimilation  of  the  moment.  In  the 
production  of  fresh  shoots  from  potatoes,  and  in  the 
germination  of  seeds,  a  large  amount  of  growth  goes  on, 
entirely  at  the  expense  of  the  food  -  reserves  stored 
away  in  the  tuber  or  seed.  It  is  only  later,  when  the 
new  shoot  has  formed  its  own  green  leaves,  that  it  can 
do  anything  at  all  towards  making  fresh  supplies  of  food 
for  itself. 

It  has  already  been  stated,  and  will  later  be  experi- 
mentally proved,  that  assimilation,  resulting  in  the 
formation  of  starch,  can  only  go  on  in  the  green  parts  of 
plants,  and  only  there  when  they  are  exposed  to  sun- 
light. The  question  naturally  arises  then :  how  do  we 
find  starch  in  tubers,  seeds,  or  other  non-green  and  even 
underground  parts  of  plants  ?  The  answer  to  this,  too, 
will  be  supplied  by  means  of  simple  experiments.  If  a 
growing  plant  is  left  exposed  to  a  good  light  from  early 
morning  to  afternoon  and  its  leaves  tested  then,  they 
will  be  found  to  be  loaded  with  starch.  But,  place  this 
same  plant  in  darkness  for  twelve  hours  or  more,  and 
its  leaves  will  be  found  to  be  almost  emptied  of  starch. 
As  a  matter  of  fact,  the  starch  formed  in  them  in  the 
sunlight  has  been  changed  into  sugar,  and  in  this  form 
carried  away  from  the  leaves  in  which  it  was  made,  and 
either  used  up  in  growth  or  often  changed  back  again 
into  starch  and  stored  up  in  some  other  part  as  a 
reserve  of  food. 


80  NATURE  TEACHING 

It  may  seem  at  first  sight  wasteful  on  the  part  of  the 
plant  to  make  starch,  then  change  it  into  sugar,  and 
often  change  this  sugar  back  again  into  starch  in  some 
other  part  of  the  plant.  We  shall,  however,  see  that 
there  is  a  reason  for  this,  inasmuch  as  only  substances 
actually  dissolved  can  be  carried  about  from  one  part 
of  a  plant  to  another ;  and  that,  as  starch  is  insoluble, 
it  has  to  be  changed  into  a  soluble  substance  (sugar) 
to  enable  it  to  be  moved  from  the  leaves  where 
it  is  formed  to  other  parts  of  the  plant  where  it  is 
needed. 

A  plant  requires  for  its  complete  nourishment  other 
food  -  substances  besides  carbon  dioxide  and  water. 
These  foods  are  mainly  nitrogen  and  mineral  matters. 
They  are  usually  obtained  from  the  soil,  being  taken  up, 
dissolved  in  water  by  the  roots.  This  watery  fluid 
which  permeates  the  plant  is  known  as  the  sap,  and  is 
in  constant  circulation  owing  to  the  evaporation  which 
we  now  know  goes  on  from  the  leaves.  As  the  result  of 
this  circulation  the  mineral  bodies  taken  up  in  the  sap 
by  the  root  are  carried  all  over  the  plant,  and,  combin- 
ing with  the  substances  formed  in  the  leaves,  are 
enabled  to  play  their  proper  part  in  the  nourishment 
and  growth  of  the  plant. 

Thus  we  see  the  leaf  is  one  of  the  most  important 
organs  of  the  plant.  By  their  leaves  plants  breathe,  and 
also  obtain  a  large  amount  .of  their  food.  The  transpira- 
tion from  the  leaves  maintains  the  circulation  of  the 
sap,  thereby  ensuring  fresh  absorption  of  mineral  matters 
by  the  root, 


THE  LEAF  81 

PRACTICAL  WORK 

Examine  leafy  shoots  of,  for  instance,  privet,  lilac, 
nasturtium,  oak,  ash,  vetch,  maple,  horse  chestnut,  sow- 
thistle,  honeysuckle,  and  any  grasses,  paying  special 
attention  to  the  leaves.  Observe  that  all  these  leaves 
have  a  thin  blade t  which  is  quite  simple  in  shape  in  the 
privet,  lilac,  nasturtium  and  grasses,  lobed  in  the  sow- 
thistle,  oak,  and  horse  chestnut,  and  divided  up,  so 
as  to  look  almost  like  a  number  of  separate  leaves,  in 
the  ash  and  vetch.  Notice  which  of  the  leaves  have  leaf- 
stalks. Make  sketches  of  all  examined. 

Examine  the  leaves  of  house-leek,  and,  if  you  live 
near  the  sea,  such  plants  as  the  sea-rocket,  sea-kale, 
sea-purslane,  or  any  other  thick-leaved  plants,  often  to 
be  found  growing  by  the  seashore  or  in  very  dry  places. 
Compare  their  leaves  with  those  above,  noting  their 
succulent  or  fleshy  character. 

Examine  also  shoots  of  furze,  heather,  broom,  or 
pine.  Notice  that  these  plants  live  in  dry  situations, 
usually  on  sandy  soils,  where  only  little  water  is  to  be 
obtained. 

Uses  of  Leaves. 

Examine  the  available  plants  (privet,  cabbage, 
lettuce,  are  very  good  examples  to  take),  and  observe 
the  delicate  young  leaves  forming  the  leaf-bud.  Notice 
how  they  are  protected  from  the  sun,  wind  and  rain,  by 
being  more  or  less  covered  over  by  the  older  leaves. 
Then  observe  the  more  elaborate  methods  in  the 
common  docks,  where  the  young  leaves  are  rolled  up 

F 


£2  NATURE  TEACHING 

inside  a  special  protecting  sheath,  and  covered  with  a 
sticky  liquid  which  prevents  them  from  drying  up.  Con- 
tinue these  observations  on  the  other  plants  to  hand. 
Carefully  sketch  all  the  buds  examined. 

Examine  shoots  of  the  common  red  clover.  At  the 
end  of  each  will  be  found  a  bud  completely  enclosed  at 
first  by  a  pair  of  greenish-white  structures,  the  stipules 
of  the  next  older  leaf,  inside  which  all  the  young  parts 
are  packed  away.  Notice  how  the  bud  gradually  opens, 
and  how  in  the  older  leaves  the  stipules  gradually  dry 
up  and  look  mere  useless  bodies.  Compare  this 
arrangement  with  the  pansy,  where  the  stipules  persist 
as  green,  leaf-like  bodies.  Examine  also  the  buds  of 
the  garden  geranium,  and  note  in  particular  how  the 
stipules,  which  look  so  small  compared  with  an  old  leaf, 
are  really  able  to  help  protect  the  leaves  whilst  these 
are  young  and  small.  Make  sketches  to  show  all  these 
arrangements,  drawing  young  leaves  protected  by  the 
stipules,  and  older  leaves  with  their  comparatively  small 
and  useless  looking  stipules  for  comparison. 

Collect,  in  the  autumn,  twigs  of  the  horse  chestnut, 
and  notice  the  large  buds.  Make  a  sketch  of  a  twig, 
showing  the  buds  and  the  scars  left  by  the  fallen  leaves. 
Examine  a  bud  more  closely,  and  notice  how  it  is 
covered  by  a  series  of  overlapping  brown  scales. 
Commencing  at  the  base  of  the  bud,  pull  off  the  scales 
one  by  one,  and  see  how  they  are  stuck  together  by  a 
sticky  resinous  material.  When  all  the  outer  scales  have 
been  removed,  examine  carefully  the  inner  portion  of 
the  bud,  and  see  that  it  consists  of  young  leaves,  beauti- 
fully folded  up  and  .packed  together  and  covered  with 


THE  LEAF  83 

white  hairs,  so  that  they  appear  to  be  wrapped  up  in 
cotton-wool. 

Watch  the  buds  through  the  winter  and  in  early 
spring.  Notice  how  on  sunny  days  they  glisten  owing 
to  the  warmth  melting  the  resinous  coating.  When 
spring  sets  in,  trace  the  gradual  swelling  of  the  buds  and 
how  finally  the  scales  are  burst  open,  and  the  young 
tender  leaves  emerge  from  their  long  rest. 

Make  similar  observations  on  the  sycamore,  apple, 
and  any  other  trees  near  to  hand.  Sketch  carefully 
buds  in  the  resting  conditions,  when  half  opened,  and 
again  after  the  young  leaves  have  expanded. 

Examine  again  the  underground  stems  of  artichoke 
and  iris,  and  observe  the  thin,  dry  scale  leaves.  In 
some  kinds  of  potatoes  similar  scale  leaves  are  well 
shown,  but  in  most  ordinary  potatoes  they  are  almost 
entirely  absent.  Note  how  they  enwrap  the  delicate, 
young,  growing  points — the  buds. 

Make  similar  observations  on  crocus  or  gladiolus 
corms,  cutting  them  through  lengthways  and  across,  and 
noting  how  the  dry  scale  leaves  wrap  over  and  protect 
the  delicate  white  buds  containing  the  ordinary  leaves 
and  flowers.  Make  sketches  to  illustrate  your  observa- 
tions. 

Examine  a  plant  of  onion  whilst  it  still  has  green 
leaves.  Note  how  it  is  wrapped  round  by  a  number  of 
dry  scales.  Look  at  the  fresh  leaves,  notice  what  their 
lower  portions  are  like,  and  see  that  in  reality  the  whole 
onion  bulb  is  composed  of  the  thickened  bases  of  leaves, 
some  of  which  are  already  above  ground  and  green, 
whilst  the  younger  ones  are  contained  in  the  centra 


84  NATURE  TEACHING 

bud.  These  points  can  be  readily  made  out  by  cutting 
onions  both  across  and  lengthwise.  Make  similar  obser- 
vations on  a  hyacinth  bulb,  and  compare  the  two  care- 
fully. 

Examine,  in  the  hedges,  shoots  of  traveller's-joy 
(common  only  on  chalk  and  limestone  districts),  and  see 
how  it  climbs  by  twisting  its  long  leaf  stalks  around 
twigs  of  other  plants.  In  addition  or  in  place  of  the 
traveller's-joy,  look  at  garden  nasturtiums,  and  see  how 
these  support  themselves  in  much  the  same  way. 
Make  a  sketch  of  a  nasturtium  holding  on  to  a  stick  or 
other  support.  Examine  the  garden  pea,  sweet  pea,  or 
wild  vetches.  In  all  these  plants  the  end  of  the  leaf  is 
prolonged  into  a  special  climbing  organ,  a  tendril,  which 
can  wrap  round  a  stick  or  string,  and  so  hold  the  plant 
up.  Compare  young  leaves  which  have  not  as  yet 
caught  hold  of  a  support  and  older  ones  which  have. 
Sketch  one  of  each. 

Structure  of  Leaves. 

Observe  the  veins  of  the  leaves  under  examination. 
See  how  much  firmer  they  are  than  the  rest  of  the  leaf; 
how  they  support  the  softer  tissue.  Hunt  among  decay- 
ing leaves  in  wet  places  under  trees,  and  try  to  find  some 
"  skeleton  "  leaves  in  which  the  soft  parts  having  rotted, 
the  hard  and  more  resistent  veins  remain  as  a  skeleton 
of  the  leaf. 

Take  some  box  leaves  and  boil  them  for  fifteen 
minutes  in  water  to  which  caustic  potash  has  been  added, 
in  about  the  proportion  of  -fa  oz.  of  the  potash  to  i  oz. 
of  water.  After  boiling,  pour  away  the  potash  and  put 


THE  LEAF  85 

the  leaves  in  a  large  dish  of  water.  Gently  brush  the 
leaves  with  a  stiff  camel's  hair  brush,  and  if  the  leaves 
have  been  boiled  enough  the  soft  parts  can  be  removed 
and  the  veins  left  forming  a  skeleton  leaf. 

With  care  it  will  be  found  possible,  on  other  leaves 
boiled  in  the  same  way,  to  strip  off  a  thin  colourless  skin 
from  the  upper  and  lower  sides,  leaving  a  middle  portion 
consisting  of  the  veins  and  the  soft  tissue.  Examine 
the  upper  and  lower  skins  with  a  hand  lens,  and  see  if 
any  of  the  minute  pores  or  stomata  can  be  made  out. 

Compare  all  the  leaves  which  can  be  obtained,  and 
note  the  arrangement  of  their  veins,  whether  netted  or 
parallel.  Examine  the  stems  of  the  same  plants  and 
see  whether,  as  a  general  rule,  you  find  stems  with 
dicotyledonous  structure  bearing  leaves  with  netted 
veins,  and  monocotyledonous  stems  parallel-veined 
leaves. 

Take  leaves  of  the  iris,  and  pull  off  a  portion  of  the 
outside  layer  of  the  leaf  (this  layer  is  very  thin  and  care 
is  required,  but  if  the  operation  is  properly  done  no 
green  tissue  will  come  away).  Note  that  the  outer  skin 
is  colourless,  that  the  underlying  tissue  is  dark  green 
and  soft,  and  has  a  number  of  hard  fibrous  structures, 
the  veins  running  through  it.  The  point  of  a  knife  can 
easily  be  got  under  one  of  these,  and  the  vein  pulled  up 
like  a  thread  of  cotton. 

Transpiration. 

Pick  a  number  of  shoots  of  any  ordinary  thin-leaved 
plants,  such  as  dead-nettle,  lilac,  groundsel.  Place  some 
in  water  and  leave  others  lying  on  the  table.  The  latter 


86 


NATURE  TEACHING 


soon  droop  and  become  limp.  Now  place  some  of  these 
in  water,  first  cutting  a  little  off  the  end  of  the  stem  to 
make  a  fresh  surface,  and  notice  that,  after  a  time,  they 
become  stiff  and  fresh  again,  whilst  those  left  on  the 
table  steadily  become  more  limp  and  at  length  wither 
and  dry  up.  Treat  in  the  same  way,  for  comparison, 

some  thick  leaves,  such  as 
house-leek,  sea -rocket,  sea- 
purslane,  etc.,  and  small- 
leaved  plants  such  as  heather, 
furze,  broom,  etc.,  and  notice 
that  these  take  a  very  long 
time  before  they  show  any 
signs  of  drying  up,  indicating 
of  what  use  to  these  plants, 
which  can  grow  in  places 
where  they  get  very  little 
water,  their  thick  or  small 
leaves  are. 

To   prove   more   directly 
that  it   is   the   leaves  which 
FIG.  8.— Experiment  to  prove  that  actually  give  off  water,  take 

leaves  give  off  water.  ... 

a  test -tube  provided  with  a 

well-fitting  cork.  Split  the  cork  lengthwise,  and  fit  the 
pieces  on  either  side  of  a  straight  leaf,  such  as  wheat  or 
daffodil  (without  cutting  off  the  leaf  or  injuring  it  in  any 
way),  and  put  the  cork  back  so  that  the  leaf  is  inside  the 
tube  as  shown  in  Fig.  8.  Let  the  leaf  remain  on  the 
plant,  and  notice  that  the  glass  inside  the  test-tube  first 
becomes  dimmed,  and  that  later  drops  of  water  trickle 
down  and  collect  at  the  bottom  of  the  tube.  It  is  not 


THE  LEAF 


87 


essential  to  use  the  leaves  mentioned  above,  any  leaf  with 
a  fairly  long  leaf-stalk  will  do  equally  well,  the  cork 
being  split  as  before  and  clipped  around  the  leaf-stalk, 
fitted  into  a  slight  groove  made  in  one  of  the  half  corks 
if  necessary. 

Take  a  plant  growing  in  a  pot,  and  do  not  water  it 
for  a  day  or  two.  The 
leaves  droop  exactly  as 
those  of  the  cuttings  left 
lying  on  the  table.  Soak 
the  pot  with  water,  and  the 
plant  revives.  These  ex- 
periments teach  us  that 
the  leaves  are  continually 
losing  water,  but  that  if 
we  supply  sufficient  water, 
either  through  the  stem 
directly,  or  indirectly 
through  the  roots,  the 
plant  will  keep  fresh. 

Take     two     tumblers 

partly    filled     with     water,    FIG.  9.— Second  experiment  to  show 

that  water  is  given  off  by  leaves. 

and    cover    each    with    a 

piece  of  cardboard  with  a  small  hole  in  the  centre  (see 
Fig.  9).  Put  through  this  hole  the  end  of  a  leafy  shoot 
— for  instance,  of  dead-nettle  or  groundsel — and  arrange 
matters  so  that  the  cut  end  of  the  stem  dips  under 
the  water.  Block  the  hole  with  wax  or  other  material. 
Cover  each  of  the  shoots  with  a  second  tumbler,  turned 
upside  down  and  resting  on  the  cardboard  covering  the 
first  Place  one  set  in  the  light  in  a  window,  and  the 


88  NATURE  TEACHING 

other  at  the  back  of  the  room  where  the  light  is  dull. 
The  inside  of  the  upper  glass  standing  in  the  window 
soon  becomes  dull  with  water  settling  on  it,  and  after  a 
time  actual  drops  of  water  will  trickle  down.  The  one 
in  the  dull  light  remains  bright  much  longer.  The  water 
which  settles  on  the  inside  of  the  glass  must  come  from 
the  plant,  for  the  card  prevents  the  water  in  the  lower 
tumbler  being  evaporated.  We  learn,  then,  as  in  our 
earlier  experiments,  that  the  leaves  give  off  water,  and 
in  addition  we  have  found  out  that  they  give  off  more 
water  when  in  the  light  than  when  in  the  dark.  Repeat 
this  experiment  with  a  shoot  from  which  the  leaves  have 
been  cut  off,  and  compare  results.  Make  sketches  of  the 
apparatus  fitted  up,  and  record  all  the  observations 
made. 

The  last  experiment  can  easily  be  modified  to  allow 
us  to  find  out  how  much  water  a  plant  actually  gives  off 
in  a  given  time.  One  method  of  doing  this  is  as  follows. 
Take  a  glazed  pot  without  a  hole  in  the  bottom — for 
instance,  an  ordinary  jam-pot — and  plant  in  it  a  young 
sunflower  or  cabbage,  in  soil.  After  two  or  three  days, 
when  the  plant  has  become  established,  water  the  plant, 
and  cover  up  the  earth  with  some  thick  tin-foil,  wrap- 
ping it  round  the  stem  of  the  plant  so  that  no  water 
can  escape  except  by  transpiration  through  the  leaves. 
Weigh  pot  and  plant  together,  and  record  the  weight 
and  the  time  in  your  note-book.  Place  the  pot  in  bright 
sunlight  in  a  window,  or  out  of  doors  if  the  weather  is 
fine,  until  the  next  day,  and  then  weigh  again.  The 
difference  in  the  two  weights  gives  the  amount  of  water 
transpired  in  this  time.  Now  lift  up  one  corner 


THE  LEAF  89 

of  the  tin-foil  and  water  the  plant ;  weigh  again,  and 
once  more  record  the  weight  Then  by  weighing  after 
another  interval  you  can  obtain  once  more  the  amount 
of  water  transpired  in  this  time.  Vary  the  experiment 
by  placing  the  plant  in  dull  light,  or  cool  places,  and  see 
what  difference  this  makes  in  the  weight  of  water  given 
off  in  a  certain  time. 

There  is  one  point  we  have  not  yet  determined, 
namely,  is  the  water  transpired  by  the  leaves  given  off 
equally  from  both  surfaces  of  the  leaf,  or  does  one  sur- 
face transpire  more  than  the  other  ?  A  simple  way  of 
testing  this  is  to  place  some  leaves  flat,  between  two 
pieces  of  glass,  and  notice  whether  one  piece  of  glass 
becomes  bedewed  quicker  than  the  other,  or  whether  both 
become  moist  at  equal  rates.  In  making  these  experi- 
ments, place  the  leaves  between  the  glasses,  and  fasten 
the  glasses  together  with  a  string  or  elastic  bands,  and 
then  stand  them  upright  so  that  both  sides  are  equally 
lighted.  Unless  this  is  done  you  would  not  be  certain 
that  any  differences  noted  were  not  due  to  one  side 
getting  more  light  than  the  other,  and  as  our  earlier 
experiments  have  taught  us,  transpiring  quicker. 

Having  found  in  the  previous  experiment  some  leaves 
which  transpire  from  one  surface  and  not  from  the  other, 
plunge  them  into  boiling  water,  and  watch  carefully  for 
small  bubbles  of  air  coming  from  them.  These  should 
appear  on  the  side  from  which  the  water  is  given  off, 
the  bubbles  coming  out  through  the  little  pores  or  stomata, 
owing  to  the  air  inside  the  leaf  getting  hot  and  expand- 
ing. In  many  leaves  the  bubbles  come  only  from  the 
lower  side. 


90  NATURE  TEACHING 

Examine  these  same  leaves  with  a  lens,  looking  care- 
fully for  the  very  small  pores.  As  the  above  experiment 
has  shown,  these  are  often  present  only  on  the  lower  sur- 
face of  the  leaf. 

Take  a  tumbler,  fill  it  half-full  of  water  coloured  with 
a  little  red  ink  or  eosin.  Place  some  leafy  shoots 
(balsams  or  lime  twigs  do  admirably)  with  the  cut  ends 
of  their  stems  dipping  in  the  water,  and  leave  them  for  a 
day  in  a  light  place  in  a  warm  room.  The  stems  become 
marked  with  red  lines,  and  finally  the  leaves  also.  This 
coloration  is  due  to  the  water  which  passes  up  the 
bundles  of  the  stem  and  their  continuation  in  the  leaves 
(the  veins),  and,  being  red,  colours  them,  thus  indicating 
the  path  in  the  stem  along  which  water  travels. 

Note  the  manner  in  which  the  leaves  of  many  grasses 
roll  up  during  very  dry  weather.  This  may  also  be 
observed  by  bringing  the  grasses  into  the  room  and 
noting  the  change  as  the  leaves  become  dry.  Observe 
the  positions  assumed  by  the  leaves  of  other  plants 
during  dry  weather,  or  at  the  middle  of  the  day  when 
the  sun  is  very  hot,  noting  whether  they  roll  up  or  droop. 
The  leaves  of  house-leeks,  laurel,  holly,  and  other  thick- 
leaved  plants  do  not  roll  up.  They  are  sufficiently  pro- 
tected by  their  thick  skin. 

Observe  during  rain,  or  while  watering  with  a  water- 
ing-can with  a  very  fine  rose,  the  direction  in  which  the 
water  is  conducted  by  the  leaves  of  the  plants  growing 
in  the  garden.  Compare  this  with  the  distribution  of 
the  roots,  and  particularly  of  the  young  rootlets  by  which 
water  is  absorbed.  Note  the  course  of  the  water  and 
the  arrangement  and  character  of  the  roots,  in — beet-' 


THE  LEAF  91 

root,  dandelion,  violets,  lettuce,  hyacinth,  and   in   trees 
such  as  the  apple,  pear,  oak,  etc. 

Plants  and  the  Atmosphere. 

Put  about  an  ounce  of  slaked  lime  (building  lime)  into 
a  wine-bottle  full  of  water  ;  shake  well  and  allow  to  settle. 
The  clear  liquid  is  lime-water,  and  should  be  carefully 
poured  off  and  kept  ready  for  use 
in  another  bottle. 

Take     a     dry     wide-mouthed  "T^"    M 

bottle,  such  as  a  jam-bottle  ;  pour         -*•*          ' — ^ 
into  it  a  little  lime-water  and  shake 
gently.     The   lime-water  remains 


J 


clear,  showing  that  in  ordinary  air 


very  little,  if  any,  carbon  dioxide 
is  present. 

Fasten  a  small  piece  of  char- 
coal  to   a   thin    wire,   ignite    the 
charcoal,    and,     using     the     wire  FIG.  10.—  Charcoal  burning 
as    a    handle,   hold    it    in   a    dry  in  glass  jar. 

wide-mouthed  bottle  similar  to  that  used  in  the  pre- 
vious experiment  (see  Fig.  10).  It  is  well  to  pass  the 
wire  through  a  cork  or  piece  of  cardboard,  so  as  to  close 
the  mouth  of  the  bottle  while  the  burning  charcoal  is  in 
it.  After  the  charcoal  has  been  burning  for  a  few  minutes 
the  flame  will  go  out,  all  the  oxygen  in  the  bottle  having 
been  used  up.  Remove  it,  pour  in  some  lime-water,  and 
shake  gently  :  the  lime-water  will  become  cloudy  owing 
to  the  formation  of  carbonate  of  lime  (chalk)  by  the  union 
of  the  lime  with  the  carbon  dioxide  produced  by  the  char- 
coal burning  in  the  oxygen  of  the  air. 


92 


NATURE  TEACHING 


Pour  a  little  lime-water  into  a  tumbler  or  small 
glass,  and  by  means  of  a  tube  (of  glass,  bamboo  or 
a  straw)  pass  the  breath  from  the  lungs  through  the 
lime-water,  which  will  soon  become  cloudy  from  the 
formation  of  carbonate  of  lime  as  in  the  last  experiment 
(see  Fig.  n).  If  the  breathing  is  continued  for  a  long 
time  the  lime-water  will  become  clear  again,  owing  to 
the  chalk  being  dissolved  in  the  excess  of  carbon  dioxide. 


FlG.  ii. — Breathing  into 
lime-water  to  show  that 
the  breath  contains  car- 
bon dioxide. 


FlG.  12.  —  Experiment  to 
show  that  plants  breathe 
out  carbon  dioxide. 


Into  a  similar  bottle,  corked  or  covered  with  a  piece 
of  glass,  place  about  a  handful  of  the  young  tips  of 
leafy  shoots,  or  opening  flower-buds — for  instance,  man- 
golds (see  Fig.  12).  Add  a  very  little  water  to  keep 
them  moist,  and  put  away  in  the  dark  for  about  six  hours. 
Test  as  before  with  lime-water,  when  it  should  be  found 
that  once  again  we  have  had  carbon  dioxide  produced 
in  considerable  amount.  Repeat  the  experiment  with 
similar  leafy  shoots,  but,  instead  of  placing  them  in  the 


(UNIVE: 

V 
^^t- 

THE  LEAF  93 

dark,  keep  them  in  strong  sunlight  out-of-doors.  No 
carbon  dioxide  should  now  be  found,  for,  as  fast  as  it  is 
formed  by  the  breathing  of  the  plant,  it  is  used  up  in 
the  process  of  assimilation. 

These  three  experiments  teach  us  that  the  processes 
of  burning  and  the  breathing  of 
animals  and  plants  agree  in  result- 
ing in    the   formation   of  carbon 
dioxide. 

Place  some  leaves  in  a  wide- 
mouthed  bottle,  fill  with  water, 
and  place  it  in  the  sunlight  (see 
Fig.  13).  Observe  that  in  a  short 
time  small  bubbles  of  gas  appear  FIG.  13. —  Experiment  to 

,11  ,.   ,  .  ,.,  show  the  bubbles  of  gas 

on  the  leaves  which  are  in  reality  given  off  from  ]eaves sin 
bubbles  of  oxygen,  formed  in  sunlight. 
the  process  of  assimilation  and  given  off  by  the  plant. 
On  repeating  this  experiment,  but  placing  the  bottle  in 
the  dark,  no  bubbles  will  be  given  off,  for,  under  these 
conditions,  no  assimilation  can  go  on. 

The  Food  of  Plants. 

Take  enough  starch  just  to  cover  a  threepenny-bit, 
drop  it  into  about  half  a  pint  of  boiling  water,  and,  when 
cold,  add  a  little  iodine  solution.  The  liquid  becomes  a 
deep  blue.  (If  you  have  too  much  starch  present  the 
colour  will  be  almost  black,  and  water  should  be  added). 
This  is  a  convenient  test  whereby  to  recognise  the 
presence  of  starch. 

Take  a  few  leaves  which  have  been  exposed  to  bright 
sunlight  for  several  hours  (fuchsias  answer  admirably), 


94  NATURE  TEACHING 

plunge  them  into  boiling  water  for  about  two  minutes, 
and  then  place  in  strong  methylated  spirits.  When  the 
liquid  has  become  of  a  deep  green  colour — owing  to  the 
leaf-green  being  extracted — pour  it  off  and  add  fresh 
spirit,  repeating  this  until  the  leaves  are  free  from  colour. 
Put  one  or  two  of  these  leaves  in  water  containing  a 
small  quantity  of  iodine  solution  ;  they  will  turn  blue. 
The  colour  will  not  be  a  pure  bright  blue,  but,  owing  to 
the  brown  stain  communicated  to  the  tissues  by  the 
iodine,  of  a  somewhat  greenish  hue. 

Take  a  plant  with  smooth  leaves — for  instance,  a 
fuchsia — growing  in  a  pot,  and  leave  it  exposed  to  the 
sunlight  from  morning  to  afternoon.  Then  cut  off  one- 
half  only  of  two  or  three  leaves,  leaving  the  other  halves 
attached  to  the  plant.  Test  the  cut-off  halves  for  starch 
as  described  above.  If  they  have  plenty,  place  the 
whole  plant  in  the  dark  until  the  next  day,  either  in  a 
cupboard  or  covered  up  by  a  box  or  tin,  taking  care 
that  no  light  at  all  gets  in.  Now  cut  off  the  remaining 
halves  of  the  leaves  tested  previously,  and  test  these  in 
exactly  the  same  way.  If  they  have  been  in  the  dark 
long  enough  (fuchsias  usually  require  only  twelve  hours, 
but  some  other  plants  take  twenty-four  hours  or  even 
longer  to  get  rid  of  all  their  starch)  they  will  be  found 
to  show  no  blue  colour,  indicating  that  all  the  starch 
they  contained  has  been  used  up  during  the  time  they 
have  been  in  the  dark. 

Using  the  plant  which  we  now  know  to  have  no 
starch  in  its  leaves,  we  can  prove  that  starch  is  only 
formed  in  the  parts  actually  exposed  to  the  light  Take 
some  tinfoil  or  lead-paper  (such  as  is  used  for  tea  pack- 


THE  LEAF  95 

ages),  cut  out  a  cross  or  other  pattern,  and  wrap  the  foil 
round  a  leaf  (attached  to  the  plant)  so  that  the  only 
portion  of  the  leaf  which  can  be  seen  is  that  which  shows 
through  the  cut-out  pattern  (see  Fig.  14).  Press  the  tin- 
foil tightly  down  on  the  leaf,  to  prevent  light  getting  under 
the  edge  of  the  cut  portion,  and  expose  the  plant  to  sun- 
light. If  this  is  done  in  the  morning  the  plant  may  be 
tested  in  the  afternoon,  and  it  should  then  be  found  on 


FIG.  14. — Experiment  to  show  that  starch  is  only  formed 
in  the  portions  of  leaves  exposed  to  sunlight.  The 
left-hand  figure  shows  the  leaf  wrapped  in  tinfoil, 
from  which  a  cross  has  been  cut.  The  right-hand 
figure  shows  the  leaf  after  exposure  to  sunlight  and 
tested  for  starch. 

boiling  the  leaf  and  decolorising  it  in  spirit,  and  putting 
it  in  iodine  solution,  that  we  obtain  a  pattern,  in  blue,  on 
the  leaf  exactly  similar  to  the  portion  exposed  to  the 
light.  That  is  to  say,  the  part  of  the  leaf  exposed  to 
the  light,  and  that  part  only,  has  been  able  to  form 
starch,  or,  in  other  words,  assimilation  only  goes  on  in 
the  light. 

The  coloration  due  to  the  iodine  soon  fades  away, 
but  the  leaves  may  be  preserved  for  any  length  of  time 


96  NATURE  TEACHING 

in  methylated  spirit,  and  the  colour  obtained  again  on 
once  more  putting  them  into  iodine  solution.  Leaves 
can  thus  be  prepared  in  the  summer  and  kept  for  use 
as  required  during  the  winter. 

Take  a  leaf  of  a  variegated  geranium  or  other  plant 
with  green  and  white  leaves,  which  has  been  in  a  good 
light  for  a  day.  Make  a  sketch  of  the  leaf,  shading  in 
the  green  parts.  Decolorise  the  leaf  by  immersing  in 
boiling  water  and  methylated  spirit,  and  then  place  in 
iodine  solution.  A  pattern  should  be  obtained  similar 
to  the  one  drawn,  showing  that  starch  is  formed  only  in 
the  green  parts  of  the  leaf,  and  that  the  white  parts 
contain  no  starch.  Draw  the  leaf  after  treatment  with 
iodine,  shading  the  blue  parts,  and  compare  it  with  your 
previous  sketch. 

The  following  experiment  will  serve  to  show  that 
unless  a  plant  is  provided  with  air  no  starch  can  be 
formed  in  its  leaves,  even  though  it  is  placed  in  the  light. 
Germinate  some  peas  and  beans,  and  after  the  first 
leaves  have  expanded,  place  the  young  plants  in  the 
dark  for  a  day.  Test  some  for  starch :  if  they  contain 
none,  they  are  ready  for  use ;  but  if  they  still  show  the 
presence  of  starch,  replace  them  in  the  dark  until  they 
are  starch-free.  Place  some  of  the  seedlings  in  bright 
light  in  a  window,  giving  water  to  their  roots  so  that 
they  do  not  dry  up.  Put  others  in  a  thin  glass  vessel 
full  of  water  which  has  been  boiled  and  allowed  to  cool 
(this  precaution  is  necessary  to  get  rid  of  the  air  dissolved 
in  the  water),  and  put  these  alongside  the  others  in  the 
window.  The  plants  should  be  weighted  with  small 
stones  to  keep  them  well  beneath  the  surface  of  the 


THE  LEAF  97 

water.  Leave  them  there  for  several  hours,  and  then 
test  leaves  from  both  for  starch.  It  should  be  found 
that  those  exposed  to  the  air  have  formed  starch,  whilst 
those  under  the  water  and  consequently  deprived  of  air 
have  formed  none. 

Another  way  of  carrying  out  the  above  experiment 
is  to  take  a  plant  the  leaves  of  which  have  been  found  to 
have  the  pores  only  on  the  underneath  surface.  Place 
it  in  the  dark  until  free  from  starch.  Then  smear  the 
under  sides  of  some  leaves  with  vaseline.  This  fills  up 
the  pores  and  prevents  air  entering  the  leaf.  Expose 
the  plant  to  sunlight,  and  after  some  hours  test  for  starch 
both  coated  and  uncoated  leaves.  The  latter  should  be 
found  to  contain  starch,  but  the  former  to  contain  none. 

We  can  now  pursue  our  inquiry  one  step  further,  and 
endeavour  to  ascertain  what  constituent  of  the  air  is 
actually  necessary  for  the  formation  of  starch.  There 
are  two  chemical  substances,  soda  lime  and  caustic 
potash,  which  have  the  power  of  absorbing  carbon 
dioxide,  and  by  using  these  we  can  obtain  an  atmosphere 
in  which  oxygen  and  nitrogen  are  both  present,  but 
carbon  dioxide  is  not.  Let  us  do  so,  and  see  if  under 
these  circumstances  a  plant  can  form  starch.  This 
experiment  can  be  arranged  as  follows : — 

Take  two  bottles  of  clear  glass  (not  tinted)  with  wide 
mouths ;  in  each  put  a  tightly-fitting  cork  with  a  bent 
glass  tube,  about  half  an  inch  in  diameter,  passing 
through  it.  In  one  of  the  tubes  put  some  lumps  of  soda 
lime,  but  leave  the  other  empty.  In  the  bottom  of  the 
bottle  fitted  with  the  tube  containing  soda  lime,  place  a 
little  dish  with  some  pieces  of  caustic  potash  in  it.  This 

G 


98  NATURE  TEACHING 

caustic  potash  will  absorb  what  carbon  dioxide  there  is 
in  the  bottle,  and  the  soda  lime  will  prevent  any  more 
entering. 

Have  ready  two  fuchsia  shoots,  which  have  been  in 
the  dark  for  a  day  and  have  been  tested,  and  are  known 
to  be  free  from  starch.  Put  the  ends  of  their  stalks  in 
little  bottles  of  water,  and  place  one  in  each  bottle. 
Replace  the  corks.  It  is  best  to  paint  the  corks  over 
with  a  coating  of  paraffin  wax  to  make  sure  that  no  air 
gets  through  them.  Put  the  bottles  thus  fitted  up,  side 
by  side,  in  the  sunlight,  and  after  say  six  hours'  exposure, 
test  a  leaf  from  each  for  starch  in  the  ordinary  way.  If 
there  is  no  appreciable  difference  leave  them  for  another 
day,  and  test  again  in  the  late  afternoon.  By  this  time 
it  should  be  found  that  the  leaves  in  the  bottle  contain- 
ing carbon  dioxide  have  formed  starch,  whilst  the  others 
have  not.  The  success  of  this  experiment  depends  on 
having  well-fitted,  good  corks,  and  on  the  glass  tubes 
fitting  tightly  in  the  corks.  Any  leakage  will  allow  air 
containing  carbon  dioxide  to  enter,  and  so  spoil  the 
experiment. 

In  the  course  of  our  experiments  we  have  repeatedly 
found  that  if  a  plant  with  its  leaves  loaded  with  starch 
is  put  away  in  the  dark  and  left  there  for  twelve  hours 
or  longer  (according  to  the  kind  of  plant  employed),  the 
starch  will  have  disappeared.  What  has  become  of  this 
starch  ?  An  answer  to  this  question  can  also  be  obtained 
by  experiment,  but  it  is  necessary  that  we  should  first 
make  some  preliminary  experiments  so  that  we  may 
understand  what  is  taking  place. 

Place  a  piece  of  starch  in  cold  water  and  let  it  remain 


THE  LEAF  99 

there  some  hours.  The  starch  does  not  disappear.  In 
other  words  it  is  insoluble  in  the  water.  Put  a  lump  of 
sugar  in  water.  It  quickly  disappears,  being  soluble  in 
water.  Starch,  then,  is  insoluble  in  water,  whilst  sugar  is 
soluble.  Soluble  substances  can  readily  pass  from  one 
part  of  a  plant  to  another.  If  now  we  can  show  that 
starch  is  changed  in  the  leaf  to  sugar,  we  can  easily 
understand  how  it  may  be  that  a  leaf  containing  starch 
in  the  afternoon  may  have  none  in  the  morning.  It  may, 
in  fact,  have  been  altered  into  sugar  and  carried  away  to 
other  parts  of  the  plant.  A  convenient  method  of  test- 
ing sugar  is  by  adding  some  to  a  solution  known  as 
Fehling's  solution,  and  boiling  for  a  minute  in  a  test- 
tube.  When  this  is  done  a  red  deposit  or  precipitate 
collects  in  the  bottom  of  the  tube,  whilst  with  starch  no 
red  precipitate  is  formed. 

Take  two  test-tubes,  and  fill  each  about  one-quarter 
full  of  Fehling's  solution.  To  one  add  a  very  little  starch, 
and  to  the  second  add  a  few  drops  of  honey.  Boil  both. 
In  the  second  a  red  precipitate  collects,  whilst  no  red 
precipitate  is  formed  in  the  first. 

Take  a  little  starch  on  the  end  of  a  penknife,  mix  it 
up  with  some  cold  water,  and  drop  it  into  about  half  a 
pint  of  boiling  water,  and  boil  for  two  minutes.  When 
cool,  add  iodine  to  a  small  portion.  It  turns  blue,  show- 
ing the  presence  of  starch.  To  a  second  small  portion 
add  Fehling's  solution,  and  boil  for  not  more  than  a 
minute.  No  red  precipitate  forms,  showing  that  no 
sugar  is  present 

Place  in  two  fresh  test-tubes  some  more  of  the  starch 
in  water,  and  add  to  each  some  saliva,  and  put  the  two 


100  NATURE  TEACHING 

tubes  in  a  glass  of  warm,  not  boiling,  water.  After  half 
an  hour  test  one  for  starch  and  the  other  for  sugar.  It 
should  be  found  that  the  starch  has  disappeared,  and  that 
sugar  has  been  formed. 

To  two  other  portions  of  starch  in  water  add  a  little 
malt  (obtained  from  a  brewery).  Keep  warm  in  the 
same  way,  and  afterwards  test  for  starch  and  sugar.  It 
should  again  be  found  that  the  starch  has  disappeared 
and  that  sugar  has  been  formed. 

Repeat  the  above  experiment,  but  instead  of  using 
malt  from  a  brewery,  take  a  good  number  (50  to  100)  of 
just-sprouted  barley  grains.  Break  off  the  young  shoots, 
and  grind  them  up  with  a  very  little  water.  Add  some 
of  this  paste  to  the  two  tubes  containing  starch,  and  keep 
just  warm  for  an  hour  or  two.  Test  the  tubes  now  for 
starch  and  sugar.  As  in  the  previous  experiments,  it 
will  probably  be  found  that  the  starch  has  gone,  and 
sugar  has  been  formed  in  its  place.  Germinating  barley, 
therefore,  contains  something  which  can  change  starch 
into  sugar. 

Gather  during  the  night  twenty  or  thirty  leaves  of 
the  garden  pea,  or  garden  nasturtium.  Rub  them  to  a 
paste  with  a  little  water,  and  add  this  liquid  to  two  more 
samples  of  starch  in  water.  Keep  warm,  and  test  after 
a  few  hours  for  starch  and  sugar.  The  same  process 
will  be  found  to  have  gone  on,  showing  that  these  green 
leaves,  like  the  germinating  barley,  contain  a  substance 
able  to  change  starch  into  sugar. 


CHAPTER   V 
THE   SOIL 

IF  we  dig  a  hole  in  the  ground  we  usually  notice  certain 
changes  in  the  appearance  of  the  earth  which  we  remove 
as  we  go  deeper  and  deeper.  That  near  the  surface  is 
often  dark  in  colour  and  loose  or  friable  ;  below  this  we 
come  in  succession  upon  material  of  a  lighter  colour, 
then  probably  a  rather  compact  layer  with  stones,  and 
finally  hard  rock.  If  we  look  at  a  place  where  a  deep 
trench  has  been  dug,  as,  for  example,  in  a  road-cutting, 
quarry,  or  excavation  for  the  foundation  of  a  house, 
or  where  a  heavy  rush  of  water  has  cut  away  the  soil, 
we  see  that  there  is  a  gradual  change  in  appearance 
from  the  upper  to  the  lower  layers.  The  stones  of  the 
lower  layers  are  probably  of  a  similar  material  to  the 
rock  at  the  bottom  ;  similarly  the  small  stones  and  even 
the  finest  particles  which  can  be  picked  out  are  often 
recognisable  as  fragments  of  the  rock  which  lies  beneath. 
In  other  words,  we  see  that  soil  largely  consists  of  rock 
broken  up  into  small  particles. 

This  breaking-up  results  from  the  action  of  various 
agencies,  but  is  very  largely  due  to  water,  containing 

carbon  dioxide  in  solution,  which  dissolves  carbonate  of 
101 


102  NATURE  TEACHING 

lime  (chalk),  and  which  also  attacks  the  mineral  known 
as  felspar,  dissolving  a  portion  of  it  and  leaving  a  residue 
which  is  clay.  A  little  search  amongst  the  stones  in  a 
garden  is  almost  sure  to  reveal  that  while  some  of  the 
stones  are  quite  hard,  others  are  relatively  soft ;  some 
being  found  which  may  be  crushed  in  the  hand,  or 
crushed  or  broken  by  the  spade.  In  these  soft  stones 
the  felspar  has  been  attacked  and  partly  converted 
into  clay.  If  the  stones  are  of  flint  or  chert  (quartz), 
these,  being  practically  indestructible,  never  become 
soft. 

Frost  is,  in  temperate  climates,  an  important  agent 
in  breaking  up  rocks  and  stones  to  form  soil.  Many 
rocks  and  stones  are  somewhat  porous,  absorbing 
appreciable  quantities  of  water.  Now,  water  expands 
in  changing  from  the  liquid  to  the  solid  state  ;  in  other 
words,  a  certain  quantity  of  water  increases  in  bulk 
when  it  is  frozen  and  changed  into  ice.  This  may  easily 
be  shown  by  filling  a  bottle  with  water,  tightly  corking 
it,  and  exposing  it  out-of-doors  on  a  cold  winter  night, 
when  the  bottle  breaks,  unless  the  glass  is  very  strong, 
in  which  case  we  usually  find  the  cork  forced  out.  The 
ice  must  get  extra  room  somehow,  and  it  is  merely  a 
question  whether  less  force  is  required  to  break  the 
bottle  or  to  force  out  the  cork.  The  bursting  of  water- 
pipes  in  winter  is  due  to  the  same  cause. 

To  return  to  the  consideration  of  a  porous  rock  ;  it 
absorbs  water,  and  if  this  water  is  subsequently  frozen  it 
expands,  and  in  doing  so  often  exerts  sufficient  force  to 
crack  the  rock.  The  cracking  due  to  any  one  freezing 
may  be  very  small,  but  when  repeated  over  and  over 


THE  SOIL  103 

again,  even  large  blocks  of  stone  are  in  the  course  of 
time  reduced  to  small  fragments. 

It  requires  little  observation  to  see  that  the  particles 
of  which  the  soil  is  composed  vary  greatly  in  size.  This 
variation  is  of  great  importance,  agriculturally,  for  the 
nature  of  the  soil  is  greatly  influenced  by  the  preponder- 
ance of  large  or  small  particles.  By  stirring  up  a  small 
quantity  of  soil  with  water  and  pouring  it  away, 
repeating  the  operation  until  the  water  comes  away 
clear,  the  fine  and  coarse  particles  may  be  separated 
from  one  another ;  and  by  stirring  up  the  water 
containing  the  finer  particles,  and  pouring  away  again, 
a  further  separation  may  be  made  into  fine  and  very 
fine  particles.  It  will  be  noticed  that  the  water  remains 
muddy  for  a  long  time,  indicating  the  presence  of 
particles  of  an  extreme  degree  of  fineness ;  these  very 
fine  particles  are  clay.  This  method,  carried  out  with 
certain  precautions,  is  largely  employed  in  ascertaining 
the  proportions  of  particles  of  various  sizes  existing  in 
soils,  and  yields  information  of  considerable  value  to  the 
farmer. 

The  particles  are  classed  as  gravel,  sand,  silt  and  clay. 

Soils  are  classed  as  gravelly,  sandy,  or  clayey, 
according  to  which  of  these  constituents  predominates. 
Gravelly  or  sandy  soils  are  often  spoken  of  as  "  light," 
not  because  they  weigh  relatively  less  than  other  soils, 
but  because  they  offer  little  resistance  to  implements  of 
tillage  (such  as  ploughs,  spades,  and  forks) ;  that  is  to  say, 
they  are  light  or  easy  to  work.  Clay  soils,  on  the  other 
hand,  are  often  called  "  heavy,"  because  of  the  difficulty 
with  which  the  implements  pass  through  them. 


104  NATURE  TEACHING 

Water  in  Soils. 

Sandy  or  light  soils  differ  in  a  marked  degree  from 
clayey  or  heavy  soils  as  regards  their  relation  to  water. 
Water  drains  through  sand  with  ease,  while  it  passes 
through  clay  soils  with  difficulty.  When  water  falls,  or 
is  poured  upon  soil,  which  is  then  allowed  to  drain,  a 
certain  quantity  of  the  water  is  retained  by  the  soil,  and 
does  not  drain  out.  Sandy  soils  retain  only  a  small 
amount  of  water,  and  clayey  soils  a  great  deal.  Thus 
sandy  soils,  while  permitting  drainage  to  take  place 
more  freely,  retain  less  water  than  clayey  soils,  and 
therefore  require  rain  more  frequently  than  clays,  or  the 
crops  growing  on  them  would  suffer  from  drought. 
Illustrations  of  these  differences,  drawn  from  his  own 
neighbourhood,  will  probably  occur  to  the  reader. 

The  explanation  of  this  retention  of  water  by  soil  is 
to  be  found  in  its  physical  structure.  There  are  spaces 
between  the  small  particles  of  soil  through  which  the 
water  passes.  Usually  these  spaces  are  filled  with  air, 
but  when  heavy  rain  comes  the  air  is  largely  replaced 
by  water,  returning  when  the  water  drains  away.  The 
better  the  tilth  of  the  soil  the  larger  will  be  the  number 
of  these  fine  air-spaces,  which  are  necessary  for  the 
maintenance  of  vigorous  plant  growth  (roots  needing 
air  as  well  as  moisture).  As  we  shall  have  occasion  to 
see  later,  important  changes,  requiring  free  access  of  air, 
are  going  on  in  every  fertile  soil.  When  water  drains 
away,  the  draining  is  never  complete,  for  soil,  after 
it  has  been  wetted,  always  retains  some  moisture, 
however  thoroughly  it  is  drained. 


THE  SOIL  105 

This  water  is  retained  by  "capillary  attraction? 
which  is  the  power  that  causes  water  to  flow  into  any 
very  small  cavities,  and  is  commonly  well  exhibited  in 
sugar,  blotting-paper,  and  similar  porous  substances. 
If  one  of  these  is  gently  brought  into  contact  with  a 
drop  of  water,  the  water  enters  the  small  pores  or 
cavities  and  spreads  over  a  large  area,  where  it  is 
retained,  and  from  which  it  will  not  drain  away  again. 
By  means  of  this  power,  soils  retain  a  sufficiency  of 
water  for  the  use  of  plants,  the  small  spaces  being  filled 
with  water  while  the  larger  spaces  contain  air.  The 
soil  is  thus  provided  with  both  of  these  requisites  for 

plant  growth. 

Clay. 

It  has  already  been  said  that  clay  is  formed  from 
felspar  by  the  action  of  water  and  carbon  dioxide. 
Pure  clay  consists  of  extremely  minute  particles,  but 
soils  are  never  pure  clay,  there  being  always  a 
certain  amount  of  sand  present.  The  fine  particles  of 
clay  have  a  tendency  to  collect  together  in  groups  or 
masses.  If  this  were  not  the  case  all  the  small  openings 
and  passages  in  the  soil  would  be  choked,  and  drainage 
rendered  impossible.  Clay  also  has  the  power  of 
absorbing  water  and  becoming  plastic ;  that  is  to  say,  it 
can  be  kneaded  and  moulded  by  the  hand,  a  property 
which  is  taken  advantage  of  in  making  bricks  and 
pottery.  When  strongly  heated,  clay  loses  this  property. 

The  operations  of  tillage  are  partly  directed  toward 
breaking  up  the  masses  of  clay,  admitting  air  into  the 
soil,  and  increasing  the  size  of  the  capillary  spaces. 
They  also  increase  the  tendency  which  the  fine  particles 


106  NATURE  TEACHING 

possess  to  gather  into  masses,  thus  permitting  a  freer 
circulation  of  water.  Lime  has  a  similar  effect  in 
causing  the  particles  to  collect  or  flocculate,  and  is  there- 
fore often  used  as  a  dressing  for  stiff,  clay  lands,  in 
order  to  make  them  lighter,  and  more  easy  to  till. 
Kneading  and  trampling  have  the  opposite  effect ; 
breaking  up  the  little  collections,  groups  or  floccules  of 
clay,  and  thus  closing  the  small  openings.  Hence  it  is 
that  brickmakers  and  potters,  who  require  firm,  compact 
masses,  thoroughly  knead  the  clay  they  use  before 
working  it  into  shape.  The  cultivator,  on  the  other 
hand,  desires  to  bring  his  clay  into  a  flocculent  condition, 
so  as  to  permit  the  circulation  of  air  and  water;  he 
thus,  at  intervals,  digs,  forks,  or  ploughs  the  soil, 
admitting  the  air  and  causing  the  clay  to  become 
flocculent,  while  he  is  careful  to  prevent,  as  far  as 
possible,  any  trampling  or  walking  over  the  soil  which 
he  has  tilled. 

Vegetable  Matter  in  Soils. 

In  digging  down  through  the  soil,  it  was  seen  that 
the  upper  layers  (surface-soil)  were  darker  than  the  lower 
(subsoil}.  This  is  due  to  the  presence  of  decaying  leaves, 
roots,  and  other  vegetable  matter  derived  from  plants 
previously  growing  on  the  spot,  or  brought  there  as 
manure.  Some  soils  are  almost  entirely  made  of  decayed 
vegetable  matter — for  instance,  in  woods  of  beech,  oak, 
etc.,  where  every  year  enormous  quantities  of  dead 
leaves  are  added  at  the  approach  of  winter.  In  swampy 
lands,  covered  with  bog  moss,  enormous  accumulations 
of  vegetable  matter  are  formed,  resulting  frequently 


THE  SOIL  107 

in  the  formation  of  peat,  which  is  almost  pure  vegetable 
matter.  If  a  little  of  the  surface-soil  is  burned,  by 
placing  it  on  a  sheet  of  iron  over  a  fire,  it  will  be  seen 
that  it  first  becomes  dark,  owing  to  the  charring  of  the 
vegetable  matter ;  then,  as  the  vegetable  matter  burns 
slowly  away,  it  becomes  lighter  in  colour,  and  more  like 
the  subsoil.  If  the  heat  be  great  and  long-continued, 
the  soil  undergoes  still  further  changes  of  colour,  often 
finally  becoming  red,  like  bricks. 

This  decaying  vegetable  matter  is  known  as  humus, 
and  is  essential  to  the  production  of  true  soil.  Mere 
crushed,  powdered,  or  disintegrated  rock  does  not  con- 
stitute true  soil,  but  requires  the  admixture  of  humus. 
Humus  plays  several  important  parts.  It  increases  the 
amount  of  water  which  sandy  soils  can  retain ;  it  tends 
to  preserve  the  porous  nature  of  stiff  clays,  facilitating 
drainage  and  admitting  more  air ;  it  assists  in  maintain- 
ing the  friable  condition  known  as  tilth  ;  and,  moreover, 
soils  rich  in  humus  do  not  become  hard  and  compact. 
It  is  worth  noting  that  the  common  expressions  "  poor 
land  "  and  "  rich  land  "  usually  refer  respectively  to  soils 
with  little  humus  and  soils  with  much  humus  in  them. 

Earth-worms  are  very  active  agents  in  distributing 
humus  through  the  soil.  They  carry  leaves  down  into 
their  burrows  and  bring  to  the  surface,  and  deposit  there, 
large  quantities  of  earth  in  the  form  of  castings.  Darwin 
estimated  that  in  an  English  meadow  the  earth-worms 
brought  to  the  surface  upwards  of  15  tons  of  earth  per 
acre  per  year.  Owing  to  this  action  of  the  earth-worms, 
objects  lying  on  the  surface  are  slowly  buried  or  appear 
to  sink  into  the  ground.  In  1842  Darwin  spread  a 


108  NATURE  TEACHING 

quantity  of  chalk  over  a  field  in  order  to  observe  at  a 
future  date  to  what  depth  it  had  been  buried.  At  the 
end  of  twenty-nine  years  a  trench  was  dug  across  the 
field,  when  a  line  of  white  nodules  was  traced  on  both 
sides  of  it  at  a  depth  of  seven  inches  below  the  surface. 
The  mould,  therefore  (excluding  turf),  had  been  thrown 
up  at  an  average  rate  of -22  (or  about  |)  inch  per  annum 
through  the  agency  of  earth-worms.  It  was  estimated 
that  the  soil  so  brought  up  in  this  meadow  weighed 
about  73,000  Ib.  From  these  and  similar  facts  it  has  of 
late  years  been  recognised  that  earth-worms  exercise  a 
very  considerable  influence  in  keeping  soils  in  a  fertile 
condition. 

Natural  processes  of  decay  lead  to  the  steady  dis- 
appearance of  humus ;  so  that  if  land  is  cultivated  and 
the  crop  steadily  removed,  there  is  a  tendency  for  the  soil 
to  become  poorer  and  poorer  as  the  humus,  originally  pre- 
sent, rots  away  and  nothing  is  added  to  replace  it.  When 
this  happens  we  hear  complaints  about  the  soil  being 
"  worn  out."  "  Wasted  "  would  be  a  better  expression.  In 
places  where  no  crop  is  removed,  as  in  woods  and  forests, 
there  may  be  a  steady  increase  of  humus  owing  to  the 
annual  addition  of  vegetable  matter  from  the  fallen  leaves 
being  greater  than  the  amount  used  up  in  a  year.  The 
soil  of  such  places,  commonly  called  leaf-mould,  is  thus 
usually  very  rich  in  humus,  and  much  sought  after  for 
purposes  of  cultivation,  on  account  of  its  fertility.  Un- 
fortunately this  fertility  is  often  rapidly  wasted  because 
the  cultivator  takes  no  pains  to  keep  up  the  supply  of 
humus. 

In  the  cultivation  of  all  soils  it  is  necessary  to  add 


THE  SOIL  109 

supplies  of  vegetable  matter  from  time  to  time,  so  that  it 
may  decay  and  become  mingled  with  the  soil  as  humus. 
Good  agriculturists  take  care  to  save  and  dig  into  their 
fields  and  gardens  all  the  available  refuse  vegetable 
matter,  such  as  manure  and  stable  refuse,  dead  leaves, 
twigs  and  grass.  We  shall  have  to  refer  to  these  later 
when  dealing  with  the  question  of  manures. 

The  very  wasteful  habit  is  often  adopted  of  burning 
a  great  deal  of  refuse  vegetable  matter  instead  of  burying 
it  in  the  soil  to  form  humus.  It  is  not  uncommon  to 
find  a  man  busily  engaged  in  burning  leaves,  and  other 
vegetable  refuse,  and  at  the  same  time  lamenting  that 
this  soil  is  becoming  worn  out.  Instead  of  being  burnt 
these  things  should  be  dug  into  the  soil,  or,  if  that  is  in- 
convenient or  impracticable,  they  should  be  thrown  into 
heaps  and  allowed  to  decay  partially.  Loss  of  valuable 
plant  food  may  be  prevented  by  covering  the  heap  with 
layers  of  soil,  which  also  prevents  the  production  of  any 
offensive  smell  or  other  unpleasantness.  Such  heaps 
are  known  as  compost-lieaps^  and  if  adopted  in  every 
garden  the  laments  about  worn-out  soil  would  cease. 
It  is  often  urged  that  by  burning  the  leaves,  twigs,  etc., 
plant  ashes  are  obtained  which  are  of  value  when  added 
to  the  soil.  This  is  true.  The  important  fact,  however, 
is  usually  overlooked  that  the  leaves  before  burning  are 
made  up,  speaking  generally,  of  ash  and  organic  matter, 
and  that  when  burnt  the  most  valuable  portion,  the 
organic  matter,  burns  away  and  is  lost.  The  ash  is  thus 
added  in  either  case,  but  by  not  burning  the  matter,  we 
add  the  most  valuable  portion,  the  organic  matter,  in 
addition. 


110  NATURE  TEACHING 

Chalk  in  Soils. 

Carbonate  of  lime,  or  chalk,  is  present  in  some  soils 
in  such  quantities,  that  they  are  distinguished  as  chalky 
or  calcareous.  Other  soils  contain  very  small  quantities 
of  carbonate  of  lime,  and  are  known  as  non- calcareous. 
A  large  portion  of  the  soils  in  Great  Britain  are  non- 
calcareous,  but  there  are  extensive  areas  where  the 
principal  rocks  are  chalk  and  limestone,  and  as  these  are 
almost  pure  carbonate  of  lime,  the  soils  formed  from  them 
are  often  very  rich  in  this  same  substance.  Examples 
of  calcareous  soils  occur  in  Kent,  Surrey,  Yorkshire, 
Norfolk,  Cambridgeshire,  Bedfordshire,  the  Isle  of  Wight, 
in  all  of  which  chalky  rocks  are  found.  A  band  of  lime- 
stone extends  right  across  England  from  Dorsetshire  to 
Yorkshire,  and  on  this  calcareous  soils  are  found. 

Calcareous  soils  are  formed  by  the  breaking  down  of 
the  chalk  and  limestone  rocks  of  these  districts. 

Carbonate  of  lime  may  be  recognised  by  the  manner 
in  which  it  effervesces  when  an  acid  is  poured  upon  it. 
This  test  may  be  used  to  distinguish  calcareous  from 
non-calcareous  soils,  the  former  effervescing,  the  latter 
not.  According  to  the  proportion  of  fine  and  coarse 
particles  entering  into  their  composition,  calcareous  soils 
may  be  either  light  or  heavy. 

Carbonate  of  lime  is  an  important  constituent  of  soils, 
because  it  takes  part  in  many  changes  which  go  on  in 
them,  as  will  be  understood  later.  Carbonate  of  lime  is 
necessary  for  the  production  of  nitrates  from  nitrogenous 
manures  ;  it  reacts  with  most  of  the  substances  employed 
as  artificial  manures,  so  that  their  application  uses  up  a 


THE  SOIL 


111 


certain  quantity  of  the  carbonate  of  lime.  There  is  thus 
a  steady,  though  small,  drain  on  the  carbonate  of  lime 
present.  This  requires  but  little  thought  when  an 
appreciable  amount  is  present  in  the  soil,  but  some  soils 
contain  so  little  that  the  addition  of  dressings  of  carbon- 
ate of  lime,  in  the  form  of  chalk  or  limestone,  at  long 
intervals,  may  be  expected  to  add  to  their  fertility. 

PRACTICAL  WORK 

Dig  a  hole  or  trench  in  the  garden,  and  note  the 
character  of  the  soil  from  the  surface  downwards  (see 
Fig.  15).  This  trench 


de- 


may  perhaps  be 
signed  to  fulfil  some 
useful  purpose,  or  the 
observations  may  be 
made  when  occasion 
arises  for  digging  thus 
deeply.  Sketch  what 
you  see. 

Ascertain,  if  possible, 
the  character  of  the  rock 
lying  beneath  the  garden 
either  by  digging  down  to  it  or  by  observing  it  at 
some  place  in  the  immediate  neighbourhood  where  it 
comes  to  the  surface,  or  is  exposed,  as  in  a  road- 
cutting. 

Collect  the  different  kinds  of  stones  to  be  found  in 
the  garden  soil,  and  note  whether  they  are  of  a  similar 
character  to  the  underlying  rock.  If  other  kinds  of 
stones  are  found,  endeavour  to  explain  whence  they  are 


IG.  15. — Diagrammatic  section  illustrat- 
ing gradual  passage  from  the  soil  to 
the  subsoil,  and,  finally,  the  underlying 
rock. 


112  NATURE  TEACHING 

probably  derived.     (A  selection  of  these  stones  should 
be  kept  in  the  school.) 

In  frosty  weather  select  one  or  two  pieces  of  sand- 
stone, and  of  brick,  of  very  porous  character.  Wash  off 
all  dust  and  loose  pieces,  place  them  in  a  vessel  of  water 
so  that  they  are  about  half  covered,  and  leave  them  to 
soak  for  two  or  three  hours.  Put  them  out  of  doors 
where  they  can  become  thoroughly  frozen,  and  allow 
them  to  remain  exposed  to  two  or  three  nights'  frosts. 
Then  bring  them  into  a  warm  room,  and  when  they  have 
thawed  completely,  examine  carefully  to  see  whether  any 
small  fragments  have  been  split  off.  The  stones  or  bricks 
should  be  placed  on  clean  plates  or  saucers  when  put 
out  in  the  cold,  in  order  that  any  small  pieces  broken  off 
can  be  more  easily  seen. 

Mechanical  Analysis  of  Soil. 

Separation  of  soil  particles  by  means  of  water  : — This 
operation  may  be  conducted  so  as  to  give  quantitative 
results  of  interest  and  value,  if  a  small  amount  of  appar- 
atus is  procurable.  For  this  work  it  is  necessary  to  have 
three  sieves  with  holes  of  known  sizes  ;  brass  sieves  with 
circular  perforations  are  preferable  to  those  of  wire. 
A  suitable  set  consists  of  three  sieves  with  holes  of 
2,  i,  and  \  millimetre  respectively.  (i  mm.  =  JT  indi-) 
A  small  scale  or  balance  for  weighing  the  separated 
gravel,  sand,  etc.,  is  also  required. 

With  these  proceed  as  follows : — From  a  well  mixed 
sample  of  soil  weigh  out  50  grammes  (if  oz.),  stir  this 
well  with  water  in  a  glass  or  cup,  and  pour  the  water 
through  the  sieve  with  2  mm.  holes  ;  the  sieve  resting 


THE  SOIL  113 

on  a  dish  or  basin.  With  successive  quantities  of  water, 
transfer  all  the  weighed  portion  of  soil  to  the  sieve. 
Gently  wash  the  particles  of  gravel  by  moving  them 
about  in  the  sieve  with  a  wooden  rod  or  stirrer  (or  a 
glass  rod  tipped  with  rubber),  using  fresh  supplies  of 
water  until  the  small  stones  are  quite  clean.  Pour  the 
water  and  soil  which  has  passed  through  the  first  sieve 
through  the  second,  similarly  supported  on  a  basin,  and 
the  water  and  material  from  the  second  through  the 
third.  Wash  the  residues  in  each  of  the  sieves  with 
gentle  stirring,  until  the  water  coming  away  ceases  to  be 
muddy.  Put  aside  the  sieves,  with  their  contents,  to  dry. 
Collect  the  washing-waters  together,  and  stir  well.  After 
standing  two  or  three  minutes  pour  away  the  muddy 
water  from  the  sandy  sediment,  wash  the  sand  into  a 
beaker  or  tumbler,  and  again  wash  with  gentle  stirring 
and  rubbing  with  the  wooden  or  rubber-tipped  rod. 
After  standing  a  short  time  once  more  pour  the  water 
from  the  sandy  sediment.  Repeat  this  process  until  the 
water  ceases  to  become  turbid. 

Dry  the  various  portions  separately  and  weigh  them  ; 
the  different  grades  may  be  designated  as  follows: — 
From  the  first  sieve,  coarse  gravel ;  from  the  second 
sieve,  gravel ;  from  the  third  sieve,  coarse  sand ;  the 
residue  from  washing,  sand.  The  amount  carried 
away  in  the  water  may  be  found  by  adding  together 
the  weights  of  the  various  grades  obtained  and  de- 
ducting this  from  the  total  weight  taken  to  be  operated 
on.  The  difference  may  be  called  silt  and  clay.  The 
quantities  should  be  calculated  in  percentages.  Samples 
of  the  separated  grades  should  be  put  into  tubes  or 

H 


114  NATURE  TEACHING 

small   bottles,   and    kept   as   a   record    and    for   future 
reference. 

This  method  gives  interesting,  and  approximately 
accurate,  results,  and  is  within  the  capacity  of  the  older 
pupils  of  a  school  class.  For  the  method  of  procedure 
where  great  accuracy  is  required,  see  such  books  as 
Wiley's  Agricultural  Analysis,  Vol.  I.  For  junior  classes 
it  is  sufficient  to  omit  the  weighing  and  to  make  approxi- 
mate separations  by  washing. 

Water  in  Soils. 

Place  in  separate  glass  funnels,  supported  over  cups 
or  tumblers,  equal  weights  of  sand,  clay  and  garden 
mould ;  these  should  be  dry  and  coarsely  powdered. 
From  50  to  100  grammes  is  a  convenient  quantity. 
Place  a  small  piece  of  blotting-paper  (or  filter-paper)  at 
the  bottom  of  the  funnel  to  prevent  the  soil  from  getting 
into  the  neck.  Shake  and  tap  the  funnel  gently  to  cause 
the  contents  to  settle  down  closely.  Now  pour  equal 
measures  of  water  on  the  contents  of  each  funnel,  using 
enough  water  to  soak  the  soil  thoroughly  and  to  allow 
water  to  drain  through  into  the  vessels  placed  beneath. 
Observe  that  the  water  flows  away  with  different  rapidity 
in  the  three  cases,  and  that  when  all  the  water  which 
will  drain  away  has  been  collected,  the  three  different 
kinds  of  soil  retain  different  amounts  of  water. 

The  funnels  with  their  contents  may  be  weighed 
before  the  water  is  added,  and  again  after  it  has  drained 
away.  The  difference  between  the  two  weighings  gives 
the  weight  of  water  retained  in  each  case,  and  the  results 
should  be  recorded  for  the  different  kinds  of  soil,  cal- 


THE  SOIL  115 

culated  for  convenience  of  comparison  to  100  parts  of 
soil. 

Fit  a  cork,  with  a  hole  in  it,  into  a  glass  tube,  about 
f  inch  in  diameter,  and  arrange  a  small  piece  of  linen  or 
blotting-paper  over  the  cork,  inside  the  tube  ;  now  pour 
shot  into  the  tube  (see  Fig.  16).  The  shot  may  be  taken 
to  represent  particles  of  soil  with  their  air-spaces.  Close 
the  opening  in  the  cork  with  the 
ringer,  and  pour  water  on  the  shot, 
fully  covering  them.  This  condition 
may  be  taken  to  represent  soil  from 
which  all  the  air  has  been  displaced  by 
water.  Remove  the  finger  ;  most  of 
the  water  will  now  drain  away,  but 
some  will  be  retained,  by  capillary 
attraction,  between  the  grains  of  shot. 
From  this  experiment  draw  inferences 
as  to  the  relation  of  water  to  small 
soil-particles. 

Place  in  a  saucer  a  little  water,  to  Fl°' 


which  a  few  drops  of  red  or  black  ink      tention  of  water  be- 

,   ,  tween  small  particles 

has  been  added  (merely  to  colour  it),      by  capillary  attrac- 

i     j.  e  .  f.       tion. 

and   dip   one    corner   of   a   piece   of 
blotting-paper   into   the   water  :   notice  how  the  liquid 
rapidly  spreads  through  the  whole  piece.     This  is  an 
example  of  the  action  of  capillary  force. 

Take  two  small  pieces  of  glass  (about  3  or  4  inches 
square)  ;  stand  them  upright  in  a  saucer  of  water  (which 
may  be  coloured  if  desired)  ;  bring  their  edges  together 
on  one  side  so  that  the  pieces  stand  like  a  partly-opened 
book  standing  on  its  edge  (see  Fig.  17).  Gradually  bring 


116 


NATURE  TEACHING 


the  open  edges  together,  as  if  closing  the  book,  and  notice 
that  the  water  rises  between  the  glasses,  being  highest 
where  the  space  between  the  glasses  is  narrowest,  and 
lowest  where  the  space  is  widest.  This  is  another  ex- 
ample of  capillary  attraction,  and  shows  that  the  effect 
is  greater  in  small  spaces  and  cavities  than  in  large  ones. 
Make  diagrams  showing  the  position  of  the  water  when 


FlG.  17.  —  Experiment  to  show  that 
water  rises,  by  capillary  attraction, 
higher  in  narrow  than  in  wide  cavities. 


FIG.  1 8. — Experiment  to 
demonstrate  the  rise  of 
water  in  soils  by  capil- 
lary attraction. 


the  glasses  are  somewhat  widely  separated  and  when 
close  together. 

Take  a  tube,  such  as  a  narrow  lamp-chimney,  tie  a 
muslin  or  linen  cap  over  the  bottom  end  and  fill  with 
soil.  Flace  the  tube,  thus  filled,  upright  in  a  saucer  of 
water,  and  note  the  manner  in  which  the  water  slowly 
rises  through  the  soil  (see  Fig  18).  This  experiment  may 
be  made  quantitative  if  the  tube  is  weighed,  before  and 
after  filling  with  soil,  to  give  the  weight  of  soil  used  ;  and 
again  after  standing  for  some  time,  say  for  twenty-four 


THE  SOIL  117 

or  forty-eight  hours,  or  until  the  water  has  risen  to  the 
top  of  the  soil,  to  ascertain  the  weight  of  water  absorbed. 
This  should  be  calculated  to  100  parts  of  soil.  If 
necessary,  water  must  be  added  to  the  saucer  from  time 
to  time  in  order  to  ensure  that  the  soil  in  the  tube  is 
always  in  contact  with  water.  Comparisons  should  be 
made  of  the  weight  of  water  absorbed  by  sand,  clay,  and 
garden-mould ;  sand  absorbs  the  least  and  clay  the 
most  water. 

The  following  experiment  will  demonstrate  the 
influence  of  capillarity  in  bringing  water  from  the  sub- 
soil to  the  surface.  Take  two  large  pots,  or  two  tubs  or 
deep  boxes,  fill  one  with  soil  in  the  ordinary  way  for 
sowing  seeds,  as  described  on  page  15.  Fill  the  other 
in  the  same  way,  but  in  filling  place  a  layer  of  fine  wire- 
gauze  horizontally  across  the  box  or  tub,  about  4  or 
5  inches  below  the  surface  of  the  soil.  This  gauze  will 
serve  to  interrupt  the  capillary  connections  between  the 
subsoil  and  the  surface.  Sow  seeds  of  barley,  grass,  or 
other  shallow-rooted  plants  (more  than  one  kind  may 
be  used)  and  place  the  boxes,  pots,  or  tubs  side  by  side 
out-of-doors.  Give  a  little  water  until  the  plants  are 
established,  and  then  leave  them  dependent  on  the 
rainfall.  Record  the  rate  of  growth  and  development  of 
the  two  sets  of  seedlings,  and  determine  the  effect  of 
restricting  the  capillary  flow  of  water.  In  a  very  wet 
season  the  pots,  etc.,  should  be  screened  from  excessive 
rainfall. 

Take  a  small  ball  of  clay — this  may  be  obtained 
from  the  subsoil  of  the  garden — let  it  dry  in  the  air  for 
a  day  or  two,  and  then  put  it  into  the  kitchen  fire  for 


118  NATURE  TEACHING 

some  hours.  When  cold,  compare  it  with  a  portion  of 
fresh,  unburned  clay.  Note  that,  although  it  is  still  able 
to  absorb  water  by  capillarity,  it  has  lost  its  plastic 
character  and  can  no  longer  be  moulded  into  shape  by 
the  hand.  Crush  it  to  powder  and  moisten  with  water ; 
the  plasticity  is  not  restored,  it  is  permanently  lost. 
Note  also  the  change  in  colour. 

Make  small  bricks  of  wet  earth,  sand  and  clay 
respectively.  Measure  and  record  their  length,  breadth 
and  thickness.  Place  the  bricks  on  a  piece  of  board  and 
put  them  on  one  side  for  a  day  or  two  until  quite  dry. 
Now  measure  them  again,  and  note  any  changes  in  size. 
Note  also  the  looseness  or  hardness  of  the  dried  bricks. 

Take  a  small  piece  of  clay,  about  the  size  of  a  hazel- 
nut,  and  rub  it  down  with  water  to  the  consistency  of 
thin  cream.  Pour  this  into  a  pint  of  rain  water  or  dis- 
tilled water  and  stir  well.  After  standing  a  minute  or  two 
pour  off  the  muddy  water  from  any  sand  which  has  settled 
to  the  bottom.  Now  take  two  similar  glass  cylinders 
or  large  tumblers,  and  fill  each  with  the  clay  water,  which 
should  again  be  stirred  before  being  poured  out.  To 
one  cylinder  or  tumbler  add  a  tablespoonful  or  two  of 
lime-water  and  stir.  Set  the  two  vessels  aside  for  the 
clay  to  settle.  Note  the  difference  in  the  way  subsidence 
takes  place  in  each,  and  recognise  that  lime  causes  the 
fine  particles  of  clay  to  collect  together  into  larger 
masses  or  floccules  which  subside  quickly. 

Vegetable  Matter  in  Soils. 

A  place  should  be  set   apart  in  the  school  garden 
for   a   compost   heap.     All  available   refuse  should  be 


THE  SOIL  119 

collected  and  placed  on  this  heap,  and,  at  intervals,  a 
layer  of  soil  should  be  thrown  over  it  to  promote  decay 
and  prevent  unpleasant  smells.  The  heap  should  be 
kept  damp  throughout.  Care  should  be  taken  to  select 
the  place  for  the  compost  heap  where  it  will  not  be 
unsightly,  and,  if  a  low  hedge  is  planted  round  the  spot, 
it  need  not  disfigure  the  neatest  garden.  It  is  convenient 
to  have  two  heaps — one  in  process  of  formation,  the 
other  ready  for  use. 

To  illustrate  the  influence  of  vegetable  matter  on 
soil  fertility,  select  in  the  school  garden  two  beds,  of 
equal  size,  with  similar  soil,  and  conveniently  near 
together  for  purposes  of  comparison.  Give  one  a  good 
dressing  of  stable-manure  (which  is  vegetable  matter  in 
a  partially-decomposed  condition),  or  a  dressing  from 
the  compost  heap,  or  of  such  material  as  grass-cuttings 
from  a  lawn  or  indeed  of  any  available  form  of  vegetable 
matter.  (There  is  a  great  difference  in  the  rates  of 
rotting  of  various  substances,  some  change  so  slowly  as 
to  be  troublesome  in  a  garden  ;  stable-manure,  owing  to 
its  being  already  partly  decomposed,  is  the  most  effec- 
tive, rotting  and  mingling  with  the  soil  rapidly.)  Give 
the  second  plot  no  manure.  Plant  similar  crops,  at  the 
same  time,  on  the  two  beds;  the  nature  of  the  crop 
adopted  depending  on  time  and  local  circumstances. 
Keep  a  record  of  the  character  and  growth  of  the  crops, 
noting  the  development  and  appearance  of  the  plants, 
the  effect  of  dry  weather  or  other  climatic  conditions. 
Note  the  weight  of  the  various  parts  yielded  by  each 
crop,  and,  from  time  to  time,  observe  the  character  of 
the  soil  of  each  plot.  These  beds  should  be  permanently 


120  NATURE  TEACHING 

established,  and  at  intervals,  perhaps  once  a  year,  the 
manured  plot  should  receive  a  dressing  of  manure  of  a 
vegetable  nature.  In  a  school  garden  a  succession  of 
lettuce,  beet,  beans,  and  cabbage  can  readily  be  grown 
on  the  beds. 

Chalk  in  Soils. 

Carbonate  of  lime — chalk.  Place  a  small  piece  of 
chalk  in  a  saucer  and  pour  upon  it  a  little  acid,  which 
may  be  strong  vinegar,  or  hydrochloric  acid.  Note  how 
it  bubbles  up,  due  to  its  giving  off  carbon  dioxide. 
Chalk  always  does  this  when  acted  on  by  an  acid,  and 
thus  this  is  a  useful  test  to  find  out  whether  a  soil 
contains  chalk  or  not.  Repeat  the  experiment,  using 
small  quantities  of  soil  from  different  places.*  From 
the  observations  made  classify  the  soils  as  calcareous 
and  non-calcareous. 

If  the  surrounding  district  contains  examples  of  both 
calcareous  and  non-calcareous  soils,  mark  their  distribu- 
tion on  a  map.  For  this  purpose  small  samples  should 
be  collected,  by  the  pupils,  from  a  number  of  localities, 
and  examined  as  a  class  exercise  or  as  a  demonstration 
by  the  teacher.  A  map  of  the  district,  on  a  somewhat 
large  scale,  may  be  drawn  on  stout  drawing-paper 
and  hung  up  in  the  class-room,  or  the  appropriate  map 
of  the  Ordnance  Survey  may  be  purchased.  Observa- 
tions on  the  character  of  the  soil  may  be  recorded,  from 

*  The  teacher  should  provide  himself  with  a  collection  of 
soils  from  different  places,  taking  care  to  have  samples  of  both 
calcareous  and  non-calcareous  soils.  These  samples  are  preferably 
kept  in  bottles. 


THE  SOIL  121 

time  to  time,  by  means  of  colours  upon  this  map,  which 
will  ultimately  become  of  considerable,  interest  if  the 
observations  are  made  carefully.  The  pupils  should 
prepare  copies  of  this  map,  on  a  smaller  scale,  for  their 
own  use. 


CHAPTER   VI 
PLANT  FOOD  AND  MANURES 

REFERENCE  has  already  been  made  to  water  and 
carbon  dioxide  as  two  of  the  constituents  of  plant  food. 
These  two  substances  are  obtained  from  the  atmo- 
sphere, the  former  falling  as  rain  and  usually  entering 
plants  through  their  roots,  the  latter  being  absorbed 
and  assimilated  by  the  green  leaves.  In  addition, 
certain  constituents  of  the  food  of  plants  are  derived 
from  the  soil.  We  may  divide  these  into  two  classes : 
nitrogenous  and  mineral  matters.  This  division  is 
convenient,  for  the  absorption  of  nitrogen  is  sufficiently 
interesting  to  make  it  desirable  to  devote  separate 
attention  to  it.  Moreover,  when  a  plant  or  any  other 
vegetable  substance  is  burned,  the  nitrogen  disappears 
in  the  gases  or  vapours,  together  with  the  carbon, 
hydrogen  and  oxygen,  while  the  mineral  matter  remains 
behind  in  the  form  of  ash. 

Nitrogenous  Matter. 

As  the  air  by  which  we  are  surrounded  consists  of 
four  parts  of  nitrogen  and  one  part  of  oxygen,  it  would 

seem   reasonable   to   suppose  that   its  nitrogen   would 
in 


PLANT  FOOD  AND  MANURES  123 

amply  provide  for  the  needs  of  plants.  Careful  in- 
vestigations, however,  have  shown  that  plants,  as  a  rule, 
are  unable  to  use  this  nitrogen  (exceptions  will  be 
referred  to  later),  but  obtain  their  nitrogen  from  the 
soil  in  the  form  of  complex  substances  known  as  nitrates. 
We  are  familiar  with  nitrates  in  the  form  of  saltpetre 
which  is  nitrate  of  potash,  and  nitrate  of  soda  largely 
used  as  a  manure. 

All  living  things,  animal  and  vegetable,  contain 
nitrogen.  When  they  decay  in  the  soil,  their  nitrogen 
is  converted  into  nitrates,  this  change  being  brought 
about  by  the  agency  of  microbes  or  bacteria  which  live 
in  the  soil  in  countless  numbers.  In  consequence  of 
the  results  they  bring  about,  these  bacteria  are  spoken 
of  as  nitrifying  bacteria.  In  order  that  they  may  live 
and  thrive  and  so  carry  on  their  useful  work,  it  is 
necessary  that  the  soil  should  present  certain  conditions. 
Moisture  and  air  are  needed,  for  in  their  absence  the 
nitrifying  bacteria  cannot  live.  A  certain  amount  of 
warmth  is  also  necessary,  the  activity  of  the  bacteria 
being  suspended,  although  they  themselves  are  not 
actually  killed,  by  the  cold  of  winter.  In  addition,  it 
is  essential  that  there  should  be  some  lime  in  the  soil. 
It  will  be  observed  that  these  conditions  are  those 
which  have  been  repeatedly  referred  to  as  the  objects 
aimed  at  in  good  tillage  and  cultivation ;  that  is  to  say, 
the  presence  of  moisture,  air,  and  lime,  together  with 
vegetable  matter  which  contains  the  nitrogen  to  be 
acted  upon.  Speaking  generally,  therefore,  we  find 
that  those  operations  and  conditions  which  render  the 
soil  best  suited  for  the  life  and  growth  of  the  nitrifying 


124  NATURE  TEACHING 

organisms  are  those  which  most  conduce  to  its  fertility. 
Practical  agriculturists  long  ago  discovered  these  facts, 
and  scientific  workers  have  now  supplied  the  explana- 
tion. 

As  plants  require  their  nitrogenous  food  to  be  in 
the  condition  of  nitrates  it  will  readily  be  understood 
that  nitrate  of  soda  is  a  valuable  source  of  plant  food, 
for  it  can  be  used  at  once  without  any  change.  Other 
substances  containing  nitrogen  are  slower  in  action  in 
proportion  to  the  time  they  require  for  the  necessary 
changes  to  take  place.  Such  bodies  are  converted  into 
nitrates,  or,  as  we  say,  nitrified,  at  very  different  rates. 
Sulphate  of  ammonia  is  very  quickly  changed,  whilst 
horn  and  leather  are  very  slowly  altered  and  are  of  less 
immediate  use  as  plant  food  on  account  of  the  slowness 
with  which  they  are  nitrified.  Most  vegetable  sub- 
stances change  with  moderate  facility,  hence  stable- 
manure,  decaying  grass,  weeds,  and  leaves  are  valuable 
sources  of  nitrogen.  Certain  animal  substances  are  also 
useful,  such  as  blood  and  refuse  from  slaughter-houses, 
the  refuse  from  fish-curing  establishments,  as  well  as 
fish  themselves,  when  caught  in  greater  abundance  than 
required  for  food. 

One  fact  demands  notice.  Many  substances,  when 
mixed  with  soil,  are  so  firmly  held  by  it  that  they  are 
not  readily  washed  out  by  rain  and  carried  away  in  the 
drainage  water.  This  is  the  case  with  phosphates, 
potash  and  ammonium  salts.  With  nitrates,  however, 
it  is  different ;  over  these,  soil  possesses  little  holding 
power,  and  they  are  easily  washed  out  and  lost.  As 
all  nitrogenous  matters  eventually  pass  into  the  form  of 


PLANT  FOOD  AND  MANURES  125 

nitrates,  it  follows  that  the  supply  of  nitrogen  in  the 
soil  is  peculiarly  liable  to  become  diminished.  This  is 
found  to  occur  in  practice,  for  nitrogen  is  usually  the 
first  item  of  plant  food  which  becomes  deficient  in  the 
soil,  and  most  of  the  efforts  of  the  cultivator,  in  the  way 
of  keeping  up  the  stock  of  plant  food,  are  directed 
towards  supplying  nitrogen. 

Leguminous  Plants  and  Nitrogen. 

It  has  just  been  said  that  plants  are  unable  to  use 
the  nitrogen  of  the  air ;  that  they  must  have  a  supply  of 
nitrogen-containing  bodies  in  the  soil ;  and  that  nitrifica- 
tion makes  these  useful  to  plants.  There  is,  however,  a 
remarkable  exception  inasmuch  as  plants  belonging  to 
the  pea  and  bean  order  (Leguminosa)  are  able  to  thrive 
in  soils  containing  no  nitrogen.  It  has  been  found  that 
this  interesting  and  important  property  is  due  to  the 
presence  of  great  numbers  of  bacteria  (microbes  or 
germs)  which  inhabit  small  nodules  or  swellings  to  be 
found  on  the  roots  of  plants  of  this  order.  The  bacteria 
living  in  these  swellings  are  able  to  feed  on  the  nitrogen 
of  the  air  and  pass  on  this  nitrogen  to  the  plants  in 
connexion  with  which  they  live.  They  thus  enable 
these  plants  to  use  the  nitrogen  of  the  air.  Now,  as 
nitrogen  is  the  most  expensive  constituent  of  plant  food, 
this  property,  possessed  by  leguminous  plants,  of  using 
and  building  up  into  their  own  structures  nitrogen  from 
the  air,  is  of  great  value  to  the  cultivator.  He  is  able 
to  grow  crops  of  beans  and  peas  upon  soils  which  are 
too  poor  in  nitrogen  to  produce  remunerative  crops  of 
other  plants.  When  the  bean  crop  is  reaped  the  roots 


126  NATURE  TEACHING 

which  remain  in  the  ground,  together  with  the  leaves, 
stems,  etc.,  may  be  returned  to  the  soil  to  increase  its 
nitrogenous  store.  The  result  is  that  the  soil  is  richer 
in  nitrogen  after  the  crop  has  been  removed  than  before. 
In  this  case  it  is  assumed  that  a  reasonable  proportion 
of  the  growth,  that  is  of  roots,  leaves  and  stems,  is  left 
upon  the  land. 

Leguminous  plants,  accordingly,  are  frequently  made 
use  of  to  increase  the  fertility  of  soils.  Crops  of  these 
plants  are  grown,  and  when  the  crop  is  well  developed, 
the  whole  of  it  is  buried  in  the  soil.  This  method 
increases  the  store  of  nitrogen  in  the  soil,  that  in  the 
crop  being  largely  derived  from  the  air.  At  the  same 
time,  it  adds  greatly  to  the  store  of  humus.  This  opera- 
tion is  usually  referred  to  as  "green  dressing"  from  the 
fact  that  in  this  method  of  working,  the  crop  is  buried 
while  it  is  in  a  green  and  fresh  condition,  instead  of 
dressing  the  soil  with  dead  or  decaying  material  of 
the  nature  of  farmyard  manure,  or  with  chemical 
substances. 

It  will  be  understood  why  it  is  more  profitable  to 
use  leguminous  plants  for  green  dressings  than  plants 
belonging  to  other  orders.  The  latter  will,  it  is  true, 
increase  the  store  of  humus,  yet  the  nitrogen  which  they 
contain  is  nitrogen  which  was  already  present  in  the 
soil.  With  leguminous  plants  there  is  a  gain  of 
nitrogen — a  constituent  which  it  is  costly  to  purchase. 

The  nitrogen  question  is  of  the  first  importance  to 
the  practical  cultivator,  a  large  part  of  his  efforts  being 
directed  towards  securing  a  sufficient  supply  of  this 
important  plant  food.  This  question  also  demands 


PLANT  FOOD  AND  MANURES  127 

especial  care  and  thought  owing  to  the  fact  that 
nitrogenous  substances  are  capable  of  many  changes, 
and  that,  if  carelessly  dealt  with,  there  are  many  ways 
in  which  nitrogen  may  be  wasted  and  lost. 

Mineral  Matter. 

Of  the  mineral  constituents  of  plant  food,  lime  has 
already  been  mentioned  ;  others  are  potash,  magnesia, 
iron,  phosphates,  chlorides  and  sulphates.  Of  these, 
potash  and  phosphates  are  often  present  in  the  soil  in 
such  small  proportions,  and  are  so  constantly  needed  by 
plants,  that  beneficial  results  follow  their  addition  to 
the  soil.  It  is  estimated  that  about  the  following 
amounts  of  potash  and  phosphoric  acid  are  removed  by 
the  crops  mentioned  : — 

Potash.        Phosphoric  Acid. 

Potato   .  .  .  .        75  Ib.  20  Ib. 

Corn  (grain  only,  30  bushels)  .  7  „  10  „ 

Manuring. 

Every  crop  taken  off  the  land  represents  so  much 
actual  weight  of  nitrogen,  phosphates  and  potash 
removed  from  the  soil.  This  fact  is  too  often  lost  sight 
of  in  practice,  and  crops  are  removed,  year  after  year, 
without  any  attempt  being  made  to  keep  up  the  supply 
of  food-stuffs  in  the  soil.  The  plants  draw  upon  the 
supply  of  food  material  present  in  the  soil,  and  thrive 
until  it  is  no  longer  able  to  satisfy  their  wants.  The 
object  of  manuring  is  to  maintain  this  supply,  or  even 
to  increase  it. 

Any  method  by  which  the  fertility  of  the  soil  can  be 
increased  may  be  included  under  the  general  term — • 


128  NATURE  TEACHING 

manuring*  Thus  thorough  tillage  of  the  soil,  and  the 
careful  maintenance  of  the  conditions  necessary  for  the 
activity  of  the  useful  bacteria,  are  in  themselves  most 
important  manurial  operations.  At  the  present  day, 
however,  the  word  manure  is  only  applied  to  the  actual 
substance  added  to  the  soil. 

Manures  may  be  classed  according  to  the  substances 
they  contain.  Thus  we  have  nitrogenous  manures, 
potassic  manures,  and  phosphatic  manures,  which  add, 
respectively,  nitrogen,  potash,  and  phosphates  to  the 
soil.  Such  substances  as  farmyard  manure  and  guano, 
which  add  all  the  requisite  substances  for  an  ordinary 
crop,  are  known  as  general  manures.  Farmyard  manure, 
guano,  etc.,  are  also  organic  manures,  being  the  direct 
product  of  living  beings,  as  opposed  to  such  substances 
as  nitrate  of  soda,  basic  slag,  etc.,  which  are  spoken  of  as 
artificial  or  cliemical  manures. 

General  Manures. 

Farmyard  manure  and  stable-manure  contain  all 
the  constituents  of  plant  food  in  well-adjusted  propor- 
tions. The  actual  amount  of  plant  food  contained  in 
these  manures  is  often  comparatively  small.  Their 
great  value  is  due  to  the  fact  that  they  add  a  large 
amount  of  organic  matter  to  the  soil.  Light  soils  are 
thus  enabled  to  retain  more  water,  and  the  crops  on 
them  to  withstand  droughts  better.  Heavy  soils  are 
rendered  more  porous  and  easier  to  work.  Such 
manures,  therefore,  are  of  great  value  to  the  cultivator, 
and  are  useful  for  almost  all  soils  and  crops.  When 
*  See  derivation  of  the  word  in  the  Glossary,  page  181. 


PLANT  FOOD  AND  MANURES  129 

manuring  has  to  be  done  on  a  large  scale  it  is  not  always 
easy  to  procure  sufficient  quantities  of  these  substances, 
and  recourse  must  then  be  had  to  artificial  manures. 

Guano  is  the  excretion  of  sea-birds,  deposited  in 
rainless,  tropical  regions.  It  contains  all  the  essential 
constituents  of  plant  food;  that  is  to  say,  nitrates, 
phosphates,  and  potash  in  a  condition  in  which  they  are 
most  readily  assimilated  by  crops.  The  nitrogen 
exists  in  various  forms,  part  ready  to  be  used  at  once 
by  the  plant,  part  requiring  to  be  changed  before  use. 
Guano  is  thus  both  lasting  and  rapid  in  its  effect. 
Rich  nitrogenous  guano  is  becoming  a  scarce  com- 
modity, and  much  of  that  now  collected  and  sold 
contains  comparatively  little  nitrogen,  but  a  considerable 
quantity  of  phosphates.  These  phosphatic  guanos  are 
very  inferior  in  value  to  the  rich  nitrogenous  ones.  In 
order  to  increase  their  usefulness  and  value,  nitrogenous 
substances  are  frequently  mixed  with  them  by  the 
dealers,  but,  even  then,  they  are  by  no  means  equal  to 
guanos  naturally  rich  in  nitrogen.  Guano,  when  stored, 
must  be  carefully  protected  from  the  rain,  as  it  readily 
spoils. 

Green  dressings  have  already  been  described.  They 
are  a  very  valuable  means  of  adding  organic  matter,  and 
the  various  constituents  of  plant  food  to  the  soil.  In 
particular  they  supply  that  most  costly  and  most  easily 
wasted  substance,  nitrogen. 

Nitrogenous  Manures. 

Sulphate  of  ammonia.  This  is  obtained  as  a  by- 
product in  the  manufacture  of  gas  from  coal,  in  the  form 


130  NATURE  TEACHING 

of  small  white  or  grey  crystals.  When  heated  with 
lime  or  other  alkali,  it  gives  off  ammonia  gas,  which  is 
easily  recognised  by  its  pungent  smell.  Sulphate  of 
ammonia  contains  about  20  per  cent,  of  nitrogen  (equal 
to  about  24  per  cent,  of  ammonia).  It  is  a  quick  acting 
manure,  although  not  nearly  so  rapid  as  nitrate  of 
soda,  and  can  be  applied  in  comparatively  large  doses 
without  risk  of  loss.  It  gives  excellent  results  on  clayey 
lands. 

Nitrate  of  soda  or  Chili  saltpetre.  This  is  obtained 
from  certain  deposits  in  Chili.  It  occurs  in  commerce 
in  larger  crystals  than  sulphate  of  ammonia,  and  has  a 
tendency  to  become  damp  by  the  absorption  of  moisture 
from  the  air.  For  this  reason  it  should  be  stored  in  a 
perfectly  dry  place.  It  may  be  recognised  by  placing  a 
fragment  on  a  piece  of  burning  charcoal,  when  it  flares 
up  and  burns.  Nitrate  of  soda  contains  upwards  of  16 
per  cent,  of  nitrogen.  It  is  very  rapid  in  its  action  ;  the 
plant  being  able  to  use  it  at  once.  It  is  readily  washed 
out  of  the  soil,  and  should  never  be  applied  in  large 
doses. 

Dried  blood  occurs  in  the  form  of  dark  brown  grains 
or  powder  containing  from  10  to  14  per  cent,  of  nitrogen. 
It  also  contains  small  amounts  of  potash  and  phosphate. 
Dried  blood,  being  insoluble,  cannot  be  used  at  once  by 
the  plant,  but  requires  to  be  altered  first.  It  is  therefore 
lasting  in  its  action. 

Phosphatic  Manures. 

Phosphate  of  lime  occurs  in  nature  (as  an  insoluble 
substance),  in  bones  and  in  certain  mineral  deposits. 


PLANT  FOOD  AND  MANURES  131 

These  are  sometimes  finely  ground  and  used  as  manure 
without  any  further  treatment,  but,  as  certain  changes 
are  necessary  before  this  insoluble  phosphate  can  be 
used  by  plants,  their  action  is  slow.  More  frequently, 
the  phosphatic  mineral,  or  the  bones,  is  treated  with 
strong  sulphuric  acid,  which  renders  the  phosphate  of 
lime  soluble.  Thus  prepared,  the  manure  is  known  as 
superphosphate.  Superphosphate  contains  from  25  to 
45  per  cent,  of  phosphate  of  lime  in  a  soluble  condition. 
Basic  phosphate,  Thomas'  phosphate,  or  basic  slag, 
is  a  form  of  phosphate  of  lime  obtained  as  a  by-product 
in  the  manufacture  of  steel.  It  is  a  heavy,  brownish  or 
purplish-grey  powder  and  should  be  as  fine  as  flour. 
Unlike  superphosphate,  which  is  acid,  basic  phosphate 
is  alkaline,  hence,  if  mixed  with  sulphate  of  ammonia  it 
will  liberate  the  ammonia.  For  this  reason  it  must  not, 
when  used  as  a  manure,  be  put  on  with  sulphate  of 
ammonia,  but  if  these  two  substances  are  to  be  applied 
to  the  same  piece  of  ground  the  basic  phosphate  should 
be  put  on  first  and  worked  into  the  soil,  and,  some  days 
later,  the  sulphate  of  ammonia  should  be  added. 

Potassic  Manures. 

Kainit.  A  mineral  obtained  from  the  Stassfurt 
mines  in  Germany.  It  consists  of  sulphate  of  potash, 
together  with  common  salt  and  Epsom  salts.  The 
actual  amount  of  potash  contained  is  usually  about 
12  per  cent. 

Sulphate  of  potash.  This  is  really  a  purer  form  of 
kainit,  containing  about  50  per  cent,  of  potash. 


132  NATURE  TEACHING 

PRACTICAL  WORK 

Burn  some  vegetable  matter — for  instance,  leaves  or 
twigs — on  a  sheet  of  iron  over  a  fire,  or  some  wood  in  a 
grate  or  stove.  Notice  that  a  large  amount  of  the 
material  disappears,  and  that  a  comparatively  small 
amount  of  ash  remains.  This  ash  is  the  mineral  matter 
of  the  plant,  the  carbon  and  nitrogenous  substances 
having  burnt  away. 

Gently  heat  a  fragment  of  wood,  a  little  starch,  a 
lump  of  sugar,  and  a  leaf,  on  a  sheet  of  iron  over  a  lamp 
or  fire.  Notice  that  all  of  them  blacken,  thus  indicating 
the  presence  of  carbon.  If  sufficient  heat  is  applied  the 
carbon  burns  away,  forming  carbon  dioxide  and  water 

(see  p.  76). 

The  Food  of  Plants. 

Take  four  ordinary  flower-pots  containing  damp 
sawdust,  and  sow  in  them  seeds  of  barley,  buckwheat  or 
other  plants.  Place  all  the  pots  in  the  dark  until  the 
seeds  have  germinated.  Now  leave  two  pots  in  the  dark, 
and  put  the  other  two  in  a  window  where  they  obtain 
plenty  of  direct  sunlight.  Water  all  as  required. 

Make  careful  notes  of  the  progress  of  the  plants  in 
each  case,  noting  whether  they  become  green  or  not, 
the  growth  each  makes,  and  how  long  they  live. 

The  experiment  may  be  made  quantitative  as  follows. 
Weigh  out  say  a  dozen  seeds  for  each  pot,  before  sowing, 
and  record  their  total  weights.  Allow  the  plants  to 
grow,  and  then  when  they  have  died  pull  them  up 
carefully,  wash  off  any  sawdust,  and  drylhem  thoroughly 
in  the  sun.  Weigh  the  twelve  plants  from  each  pot,  and 


PLANT  FOOD  AND  MANURES  133 

compare  their  total  weight  with  that  of  the  twelve  seeds 
sown  in  the  pot. 

This  experiment  should  teach  us  that  plants  cannot 
thrive  very  long  if  supplied  with  nothing  else  but  water, 
for  they  are  unable  to  make  any  use  of  sawdust  as  a 
food. 

When  plants  are  grown  under  these  conditions,  does 
it  make  any  difference  whether  they  are  in  the  light  or 
not?  This  experiment  if  carried  out  carefully  should 
answer  this  question. 

The  above  experiment  can  be  usefully  extended  by 
growing  some  plants  in  sawdust  with  the  addition  of 
water  only,  others  in  sawdust  watered  with  a  solution 
containing  all  the  essential  things  for  plant  growth,  and 
others  in  ordinary  good  soil. 

A  useful  plant  food  solution  for  this  purpose  is  the 
following : — 

Calcium  nitrate  .  4  grammes  or  about  60  grains. 

Potassium  nitrate         .  I  gramme         „         15      „ 
Magnesium  nitrate       .  „  „         1 5       „ 

Potassium  phosphate    .  „  „         15       „ 

Iron  chloride         .        .  one  or  two  drops. 

Water  ....  3  litres  or  about  5  pints. 

Place  as  before  some  plants  in  the  dark,  and  others 
in  sunlight,  and  note  carefully  their  growth  and  appear- 
ance in  each  case.  Also  dry  and  weigh  a  certain 
number  of  seedlings  from  each  set  of  experiments,  and 
compare  their  weights. 

These  two  sets  of  experiments  should  teach  us  the 
importance  of  light  and  plant  food  to  the  life  and  growth 
of  plants. 


134  NATURE  TEACHING 

Experiments  with  Manures. 

By  cultivating  plants  in  boxes  or  in  isolated  garden 
plots,  experiments  may  be  made  as  to  the  action  of  the 
various  manures  in  common  use.  The  soil  of  an  ordinary 
garden  is  usually  fairly  well  supplied  with  all  the  necessary 
constituents  of  plant  food.  In  order  therefore  to  obtain 
immediate  and  striking  proof  of  the  effects  of  manures, 
it  is  advisable  to  use  poor  soil.  Sand  is  very  convenient, 
and,  if  obtainable,  should  be  employed.  In  most  local- 
ities accumulations  of  sand  suitable  for  the  purpose  can 
be  found,  for  instance,  on  the  sea-beach  or  in  beds  of 
streams.  The  sand  used  should  be  free  from  salt.  Before 
using  it,  therefore,  it  is  advisable  to  wash  it  thoroughly  to 
remove  the  salt.*  The  manner  of  doing  this  will  depend 
on  the  facilities  at  hand.  A  convenient  method  is  to 
put  the  sand  into  a  barrel,  the  bottom  of  which  has  a 
number  of  holes  bored  in  it,  and  to  pour  water  on  it. 
The  water  will  drain  away  through  the  holes,  and  carry 
the  salt  and  other  soluble  matters  with  it. 

Pure  sand  is  a  very  unfavourable  soil  for  plants,  and 
a  small  amount  of  moss  litter,  not  more  than  i  per  cent, 
should  be  added  to  it. 

Take  four  boxes,  about  2  feet  long,  2  feet  broad,  and 
9  to  12  inches  deep.  Bore  a  few  holes  in  the  bottom  of 
each  to  allow  of  drainage.  Place  them,  side  by  side  in 
a  hole  dug  in  the  garden,  with  not  more  than  an  inch  of 
the  box  projecting  above  the  surface  of  the  soil.  By  so 

*  Washing  is  unnecessary  if  one  is  reasonably  sure  of  the 
absence  of  salt ;  washing  is  more  particularly  referred  to  in  case 
sea-sand  is  used. 


PLANT  FOOD  AND  MANURES  135 

placing  the  boxes,  excessive  evaporation  from  the  soil  in 
them  is  prevented.  A  well-drained  spot  should  be 
selected  for  the  boxes  in  order  to  guard  against  water 
accumulating  under  and  around  them.  If  the  soil  is 
very  clayey  this  object  may  be  secured  by  putting  under 
each  box  a  layer  of  small  stones.  It  is  also  necessary  to 
arrange  the  boxes  so  that  the  drainage-water  from  one 
will  not  run  under  the  next.  Mark  the  boxes  A,  B,  C, 
and  D. 

In  all  such  experiments  too  much  care  cannot  be 
taken  to  secure  uniform  conditions  for  the  boxes  or 
plots  to  be  experimented  upon.  For  instance,  if  one 
box  is  shaded  and  another  not,  and  they  are  treated 
differently  as  regards  manuring,  it  is  impossible  to  be 
certain  afterwards  whether  any  difference  in  their  crops 
is  due  to  the  different  manures  used  or  to  the  difference 
of  lighting. 

Fill  the  boxes  with  the  washed  sand,  and  to  this 
add  the  various  substances  whose  effects  we  wish  to 
try. 

To  the  soil  in  A,  add  nothing.     This  is  the  control 

or  standard. 

To  B,  add  about  8  Ib.  of  well-rotted  farmyard  or  stable 

manure.     Carefully  fork  the  manure  into  the  sand,  or 

remove  the  soil  and  mix  the  manure  with  it  in  a  dry 

place,  and  then  return  to  the  box. 

To  C,  add  2  oz.  of  finely-powdered  chalk  or  marl, 

scattering  it  evenly  over  the  surface,  and  stir  in  lightly 

with  a  fork.     Then  add  J  oz.  of  sulphate  of  ammonia. 
To  D,  add  about  2  oz.  of  finely-powdered  chalk  or 

marl ;  mix  well,  and  then  apply  J  oz.  basic  slag,  J  oz. 


136  NATURE  TEACHING 

sulphate  of  potash  and  \  oz.  sulphate  of  ammonia.* 
Scatter  these  substances  evenly  over  the  surface,  stirring 
each  in  before  the  next  is  added.  Dig  in  the  basic  slag 
somewhat  deeply. 

Finally,  spread  an  ounce  of  moist  garden  soil  over 
each,  in  order  to  ensure  the  presence  of  the  nitrifying 
organisms  which  would  probably  be  absent  from  the 
washed  sand. 

If  it  is  convenient  to  make  plots,  treat  these  in 
exactly  the  same  way,  taking  similar  precautions  with 
regard  to  situation  and  drainage,  as  observed  in  the  case 
of  the  boxes.  The  amounts  given  above  are  for  boxes 
of  the  size  mentioned,  2  feet  long  by  2  feet  broad,  that 
is  with  a  surface  of  4  square  feet.  Larger  or  smaller 
boxes  would  require  correspondingly  larger  or  smaller 
quantities  of  manure.  Similarly,  a  bed  8  feet  long  by  3 
feet  broad,  or  24  square  feet  in  surface,  would  require 
six  times  the  amounts  given.  The  four  boxes  or  plots 
now  stand  as  follows  : — 

A.  No  manure. 

B.  Farmyard  or  stable  manure,  at  the  rate  of  about 

30  tons  per  acre. 

C.  Nitrogen  only,  as   sulphate   of  ammonia,  about 

2  cwt.  per  acre. 

D.  Nitrogen  as  sulphate  of  ammonia,  about  2  cwt. 

per  acre,  together  with  potash  and  phosphate. 
Raise  in  each  box,  or  on  each  plot,  a  similar  crop. 
Barley,  wheat,  oats,  turnips,  beet  or  cabbage,  are  recom- 

*  In  accordance  with  what  has  been  said  before,  it  is  advisable 
to  add  the  sulphate  of  ammonia  about  a  week  after  the  lime  or 
basic  slag  has  been  applied,  to  prevent  the  loss  of  the  ammonia. 


PLANT  FOOD  AND  MANURES  137 

mended.  The  seeds  may  be  sown  in  the  boxes  them- 
selves, and  when  they  have  germinated  an  equal  number 
of  vigorous  and  well-placed  seedlings  kept  in  each  box 
Carefully  pull  up  all  the  seedlings  not  wanted.  If  trans- 
planted into  the  boxes,  put  in  each  the  same  number  of 
seedlings,  as  far  as  possible  equal  in  size  and  vigour. 
Care  is  just  as  necessary  here  as  in  arranging  the  boxes 
at  first  The  ideal  to  aim  at  is  to  have  the  boxes  or 
plots  exactly  alike  in  everything  except  the  actual 
manure  added.  Make  and  record  observations  during 
the  growth  of  the  crops,  noting  the  general  vigour  and 
character  of  the  plants  in  each  box,  their  times  of  flower- 
ing, and  any  other  points.  When  they  are  mature  dig 
up  and  weigh  the  whole  crops,  recording  the  weight  of 
seed  and  the  weight  of  the  whole  plant.  Compare  the 
crops  of  the  different  boxes. 

Leguminous  Plants. 

Sow  in  boxes  or  in  plots,  seeds  of  various  plants  of 
the  leguminous  order;  for  instance,  various  kinds  of 
beans,  peas,  etc.  (Those  sown  in  the  experiment  de- 
scribed on  page  21  will  probably  be  at  hand,  and  if  so 
may  well  be  examined  now.)  When  the  plants  have 
become  well  developed,  carefully  dig  them  up,  wash  their 
roots,  and  examine  for  nodules.  These  appear  as  little 
swellings  along  the  roots,  varying  from  about  the  size 
of  mustard  seed.  Also,  dig  up  and  examine  for  nodules 
any  leguminous  plants  found  growing  wild.  Many  may 
be  recognised  by  the  great  resemblance  of  their  flowers 
to  those  of  the  garden  peas  and  beans,  and  by  their 
similarly  divided  leaves.  Study  therefore  the  look  of 


138  NATURE  TEACHING 

the  leaves  and  flowers  of  such  garden  leguminous  plants 
as  you  have,  and  then  dig  up  similar-looking  plants  found 
growing  wild. 

Make  two  or  three  plots  in  the  garden,  taking  the 
precautions  previously  described.  Weed  and  dig  the 
plots  carefully.  Plant  nothing  at  all  on  the  first  plot, 
but  keep  it  free  from  weeds ;  that  is,  in  the  state  known 
as  bare  fallow.  On  the  others  sow  some  leguminous 
crop  (peas,  field  beans,  lupines).  Tend  the  plants  care- 
fully until  they  produce  a  good  growth  of  foliage,  and 
cover  the  ground  well.  Then  pull  up  the  plants  by  the 
roots,  dig  up  the  ground  and  bury  the  whole  growth  in 
the  plot  in  which  it  grew.  The  crop  should  be  buried 
whilst  still  green,  and  not  allowed  to  remain  until  it 
becomes  old  or  woody. 

After  the  green  dressing  has  been  buried  several 
weeks,  plant  all  the  plots,  including  the  one  which  was 
kept  bare  and  received  no  green  dressing,  with  such  a 
crop  as  wheat,  barley,  turnip,  beet  or  cabbage,  and 
observe  the  varying  growth  on,  and  the  crop  produced 
from,  the  various  plots.  If  a  poor  piece  of  ground  is 
chosen  for  this  experiment  the  results  will  be  the  more 
striking. 


CHAPTER   VII 

FLOWERS  AND   FRUITS 

MOST  plants — for  example,  those  raised  from  the  seeds 
sown  during  the  work  of  Chapter  I. — if  kept  under 
observation,  are  found  to  pass  through  well-marked 
stages  in  their  life-history.  For  some  time  they  grow, 
producing  only  new  stems,  leaves,  and  roots.  Sooner 
or  later  they  begin  to  form  flowers,  which  appear 
first  as  flower-buds,  later  as  open  flowers.  After  the 
flowers  have  been  open  for  some  time,  certain. parts  of 
them  wither  away,  but  some  portions  remain  and,  later, 
fruits  containing  seeds  may  be  expected  to  be  found. 
Clearly,  fruits  and  seeds  are  dependent  on  and  result 
from  flowers.  Everyday  experience  tells  us  that  it  is 
useless  to  look  for  beans  on  a  bean  plant  before  it  has 
flowered.  In  the  present  chapter  we  shall  try,  first  of 
all,  to  understand  what  a  flower  is,  of  what  parts  it  is 
made,  of  what  use  these  parts  are,  and  how  fruits  and 
seeds  are  formed  from  flowers. 

Parts  of  a  Flower. 

Flowers  at    first   sight   vary  very  much  in  appear- 
ance ;  they  are  of  different  colours,  sizes   and  shapes. 


140  NATURE  TEACHING 

When,  however,  we  examine  them  more  closely,  we  find 
that  a  very  large  number  are  built  up  on  a  similar  plan 
just  as  we  found  the  various  kinds  of  leaves  to  agree 
in  essential  parts.  In  selecting  the  first  flowers  for 
examination  it  is  important  to  choose  those  whose  parts 
are  large,  simple,  and  not  too  numerous.  A  tulip  or 
any  of  the  ordinary  garden  lilies  affords  an  excellent 
example. 

In  a  lily  or  tulip  flower  the  following  parts  can  be 
made  out:  Six  large  (white,  yellow,  or  red)  leaf-like 
bodies — the  petals  which  make  the  outside,  showy  por- 
tion of  the  flower.  They  are  obviously  arranged  in  two 
rings,  three  being  inside  and  three  outside.  Inside  these 
come  six  bodies,  each  consisting  of  a  stalk  with  a  swollen 
portion  at  the  free  end.  These  are  the  stamens,  the  end 
portion  of  each  of  which  is  full  of  a  yellow  powder,  the 
pollen,  which,  when  the  stamens  are  ripe  and  open,  is 
exposed.  In  the  midst  of  the  stamens  is  another  body, 
bearing  no  pollen-box  at  its  upper  end,  but  swollen 
out  beneath  into  a  green  structure,  which,  if  cut  across, 
is  found  to  be  divided  into  three  compartments,  each 
containing  a  large  number  of  small  white  bodies,  the 
future  seeds.  This  swollen  portion  is  the  ovary  and  the 
little  white  bodies  it  contains  are  the  ovules. 

Flowers  of  the  common  meadow  buttercup  or  crow- 
foot may  well  be  examined  after  we  have  made  out 
the  structure  of  such  a  large  and  simple  flower  as  the 
lily  or  tulip.  Buttercups  have  the  advantage  of  being 
very  common  and  obtainable  practically  all  the  year 
round.  On  the  outside  there  is  a  ring  of  five  greenish- 
yellow,  hairy  bodies,  the  sepals.  Inside  these  is  another 


FLOWERS  AND  FRUITS  141 

ring,  of  five  petals ;  these  are  much  larger  than  the 
sepals,  and  of  a  bright  shining  yellow  colour ;  within  the 
petals  are  a  large  number  of  stamens,  which,  although 
much  smaller  than  those  of  the  lily,  consist  of  the  same 
parts — a  thin  stalk  with  a  swollen  portion,  the  pollen- 
box  at  the  free  end.  In  the  centre  of  the  flower,  instead 
of  the  single  large  ovary  of  the  lily,  are  a  large  number 
of  little  green  bodies,  slightly  swollen  below,  and  ending 
in  a  thinner,  hooked  portion.  By  examining  an  older 
flower,  one  from  which  the  petals  have  dropped  off,  we 
shall  find  that  these  little  green  bodies  have  grown,  and 
become  hard  and  brown,  and  that  with  care  we  can  open 
them  and  see  that  each  contains  one  seed.  These  green 
bodies  are  in  reality  the  ovaries  containing  each  one 
ovule,  and  correspond  to  the  large  ovary  of  the  lily 
flower.  The  thin  curved  portion  of  each  little  ovary  is 
the  style,  and  spreads  out  at  the  end  into  a  wider  body, 
the  stigma.  Overlooking  thus  for  the  time  all  the 
differences,  we  find  that  the  buttercup  agrees  with  the 
lily  and  tulip  in  possessing  petals,  stamens  containing 
pollen,  and  ovaries  enclosing  the  ovules  which  later 
develop  into  seeds. 

Other  flowers  will  show  other  variations  in  arrange- 
ment of  parts.  In  the  harebell  or  Canterbury  bell  the 
large  blue  portion  obviously  corresponds  to  the  petals  of 
the  buttercup.  It  is,  however,  all  in  one  piece,  and  only 
the  lobing  at  the  top  reveals  the  fact  that  it  really 
represents  a  number  of  separate  petals.  In  some  other 
plants — for  instance,  the  primrose — the  petals  are  joined 
up  so  as  to  form  a  narrow  tube  below,  spreading  out 
above,  however,  in  five  large  lobes.  Notwithstanding 


142  NATURE  TEACHING 

these  differences,  all  these  flowers  have  the  same  general 
plan  : — 

(1)  Outer  leafy  bodies  which  may  be  all  alike  as  in 
the  lily  and  tulip,  or  divided  into  two  more  sets  as  in  the 
buttercup.     When  the  latter  is  the  case  we  often  find 
only  the  inner  row,  the  petals,  coloured ;  and  the  outer 
row,  then  called  sepals,  green.     Petals  and  sepals  may 
be  separate,  or  joined  up  so  as  to  form  cup-like  or  tube- 
like  flowers. 

(2)  Stamens,  each  consisting  of  a  stalk,  and  a  knob 
containing  pollen. 

(3)  The  pistil,  consisting  of  a  lower  swollen  portion, 
the  ovary  (containing  the  ovules),  and  an  upper  portion, 
the  style,  which  may  be  long  or  short,  and  often  ends  in 
a  more  or  less  hairy  or  sticky  stigma. 

The  lily,  tulip,  and  buttercup  have  all  these  parts 
contained  in  one  and  the  same  flower.  They  are  examples 
of  perfect  or  complete  flowers.  The  cucumber  or  vegetable- 
marrow  flower,  on  the  other  hand,  is  different.  If  a 
flowering  plant  of  either  of  these  is  carefully  looked  over, 
two  kinds  of  flowers  may  be  distinguished — even  whilst 
in  the  bud  stage.  Both,  when  open,  are  large  and  have 
a  yellow  cup  of  petals.  The  centre  of  one  is  occupied  by 
a  yellow  column  which  is  covered  with  pollen.  The  other 
kind  of  flower  has  its  centre  taken  up  with  a  large,  lobed 
body,  the  stigma,  sticky  and  covered  with  short  hair; 
and  beneath  the  yellow  petals  is  a  swollen  portion  (obvi- 
ously a  very  young  cucumber  or  marrow),  the  ovary. 
We  have,  in  fact,  here  stamens  and  pistil  in  separate 
flowers,  which  are  respectively  described  as  staminate 
and  pistillate. 


FLOWERS  AND  FRUITS  143 

Uses  of  the  Parts  of  a  Flower. 

Plants,  such  as  the  cucumber,  in  which  the  stamens 
and  pistils  are  in  separate  flowers,  are  very  convenient  to 
employ  in  endeavouring  to  understand  the  uses  of  the 
various  parts.  Keeping  a  cucumber  plant  under  obser- 
vation, we  find  that  cucumbers  are  never  borne  on  the 
staminate  flowers,  but  always  on  the  pistillate  flowers. 
Of  what  use,  then,  are  the  staminate  flowers  ? 

Experiments  have  often  been  made  (and  any  one 
with  care  can  repeat  them),  which  clearly  show  that  both 
staminate  and  pistillate  flowers  play  a  part  in  the  pro- 
duction of  seeds  and  fruit.  A  pistillate  flower,  tied  up 
just  before  it  opens,  in  a  thin  paper  bag,  and  kept  tied  up, 
forms  no  fruit,  but  its  ovary  shrivels  up  and  withers  like 
the  rest  of  the  flower.  A  second  pistillate  flower,  also  tied 
up  before  it  has  opened,  but  which  when  open  has  had 
some  pollen  from  a  staminate  flower  put  on  its  stigma, 
forms  fruit.  The  petals  of  this  flower  wither  up  like  the 
first,  but  its  ovary  does  not,  but  commences  to  grow  and 
finally  forms  a  ripe  fruit  with  seeds  in  it. 

Thus  we  learn  that  for  the  production  of  fruit  and 
seeds,  it  is  necessary  for  the  stigma  of  the  flower  to  have 
some  pollen  of  the  same  kind  of  plant  placed  upon  it 
When  this  has  been  done  the  flower  is  said  to  ^pollinated. 
The  actual  events  which  take  place  as  the  results  of  pol- 
lination cannot  be  studied  without  more  apparatus  than 
is  at  our  disposal.  They  will  be  found  fully  described 
and  illustrated  in  most  botanical  text-books.  The  final 
result  of  pollination  is  the  fertilisation  of  the  flower,  and 
only  when  this  has  happened  are  seeds  formed.  Pollina- 


144  NATURE  TEACHING 

tion,  the  actual  placing  of  the  pollen  on  the  stigma,  and 
fertilisation  resulting  from  this,  are  two  perfectly  separ- 
ate processes,  and  should  be  clearly  distinguished. 

The  other  parts  of  a  flower  may  be  naturally  absent, 
or  artificially  removed,  without  hindering  the  formation  of 
fruit.  They  are  not  essential.  Stamens  and  pistil  are 
essential,  for  without  them  no  seeds  can  be  formed.  Not 
only,  too,  must  they  be  present,  but  unless  the  stigma 
receives  upon  it  some  pollen,  no  seeds  will  be  formed. 

Sepals  and  petals  are  of  use  in  other  ways.  The 
sepals  usually  protect  the  more  delicate  and  important 
parts  when  young.  They  cover  the  flower-buds  and  act 
in  a  very  similar  manner  to  the  scale  leaves  which  pro- 
tect the  leaf-buds  in  many  plants.  The  petals  usually 
make  the  showy  part  of  the  flower,  and,  as  we  shall  see 
later,  are  of  great  use  in  helping  to  attract  insects.  They 
are  aided  in  this  by  the  sweet  smell  of  so  many  flowers, 
and  also  by  the  presence  of  honey,  which  is  well  known 
to  be  very  commonly  present  in  flowers,  and  in  most  of 
those  already  discussed  is  to  be  found  in  fairly  large 
amounts. 

To  sum  up,  we  find  that  in  flowers  the  stamens 
and  pistil  are  essential  to  the  production  of  seed.  The 
sepals  and  petals  are  not  essential ;  the  former  acting  as 
a  protective  covering  to  the  young  flower,  and  the  latter 
having  other  uses  in  relation  to  insects. 

Insects  and  Flowers. 

Still  bearing  in  mind  such  a  case  as  the  cucumber,  we 
have  next  to  discover  how  the  pollen  finds  its  way  from 
a  staminate  flower  to  the  stigma  of  a  pistillate  flower, 


FLOWERS  AND  FRUITS  145 

which,  although  on  the  same  plant,  may  be  several  feet 
or  yards  away.  Those  who  grow  cucumbers  know  that 
it  is  not  actually  necessary  to  go  to  the  trouble  of  putting 
pollen  on  the  stigmas  ;  yet  fruits,  containing  good  seeds, 
are  regularly  formed.  There  must  be  some  way  therefore 
in  which  pollen  naturally  gets  from  one  flower  to  another. 

Careful  watching  of  a  bed  of  cucumbers  will  often 
show  that  the  open  flowers  have  various  visitors.  Bees 
come  to  the  flowers,  go  down  to  the  bottom  where  the 
honey  is,  and  if  it  is  a  staminate  flower,  have  in  so  doing 
to  push  past  the  column  in  the  middle  which  is  covered 
with  pollen.  As  a  result  they  come  .out  with  a  large 
amount  of  pollen  on  them.  Such  a  bee,  if  watched,  will 
probably  be  found  to  visit  another  cucumber  flower.  If 
the  second  one  is  also  a  staminate  flower  it  simply  gets 
more  .pollen  on  itself.  If,  however,  it  goes  to  a  pistillate 
flower,  that  portion  of  itself  which  has  become  covered 
with  pollen,  now  rubs  against  the  stigma,  to  which,  being 
sticky,  some  of  the  pollen  adheres.  Thus  we  see  that 
insects  play  a  very  important  part  in  the  carrying  of 
pollen  from  one  flower  to  another.  The  importance  of 
this  work  of  bees  and  other  insects  to  flowers  cannot  be 
overestimated,  and  it  requires  very  little  observation  to 
see  how  general  it  is.  Besides  bees,  butterflies  and 
moths  carry  on  the  same  work.  An  owner  of  an  orchard 
of  apples  or  cherries,  for  example,  who  keeps  bees,  may 
not  only  directly  profit  by  the  honey  they  yield,  but  also, 
perhaps  to  a  much  greater  extent,  by  the  increased 
amount  of  fruit  he  obtains  from  his  trees,  due  to  their 
visits. 

It  might  at  first  be  thought  that  whilst  the  visits  of 

K 


146  NATURE  TEACHING 

insects  were  absolutely  necessary  to  plants  in  which  the 
stamens  and  pistils  were  not  in  the  same  flower,  that 
they  were  unnecessary  to  those  plants  (by  far  the 
greater  number)  in  which  both  these  essential  organs 
are  in  the  same  flower.  This,  however,  is  not  so.  The 
stamens  and  pistils  of  such  "  complete  "  flowers  commonly 
ripen  at  different  times,  so  that  when  the  stigmas  are 
ready  to  receive  pollen,  the  stamens  of  that  particular 
flower  have  already  shed  their  pollen.  In  other  cases 
various  arrangements  are  found  whereby  the  pollen  of  a 
flower  is  prevented  from  reaching  the  stigma  of  the  same 
flower.  The  result  is  that  cross-fertilisation ,  the  fertilisa- 
tion of  a  flower  by  the  pollen  of  another  flower,  is  the 
general  rule,  and  self-fertilisation — that  is,  by  the  pollen 
of  the  same  flower — is  comparatively  rare  even  in  plants 
which  have  both  stamens  and  pistils  in  one  flower. 

Many  flowers  can  be  pollinated  by  almost  any  insect. 
Others  have  very  complicated  arrangements,  and  are 
specially  adapted  to  particular  insects.  This  is  well 
illustrated  by  the  flower  of  the  vanilla  plant  (a  climbing 
orchid,  grown  in  many  parts  of  the  tropics),  which  is  so 
elaborately  made  that  it  must  be  visited  by  certain 
insects  before  it  can  be  pollinated  naturally;  and,  as  these 
particular  insects  are  not  found  in  most  of  the  countries 
where  vanilla  is  now  grown,  the  cultivator  of  vanilla,  in 
order  to  be  certain  of  obtaining  pods,  has  to  place  pollen 
upon  the  stigma  of  every  flower  by  hand. 

Wind- Pollinated  Flowers. 

As  a  general  rule  the  flowers  visited  by  insects 
are  brightly  coloured,  sweet-scented,  and  secrete  honey. 


FLOWERS  AND  FRUITS  147 

Some  have  all  three  of  these  characters ;  others  only  one 
or  two  of  them.  There  are,  however,  a  large  number  of 
flowers  which  are  not  brightly  coloured,  have  no  sweet 
scent,  and  secrete  no  honey.  The  flowers  of  cereals 
and  grasses — for  instance,  wheat,  barley,  and  ordinary 
grasses,  hazels,  many  willows,  pine  trees,  etc. — are  good 
examples.  Insects  do  not  visit  them  much,  and  their 
pollen  is  carried  from  one  flower  to  another  by  the  wind. 

In  these  wind-pollinated  flowers  attractions  to  make 
insects  visit  them  are  absent ;  but  instead  they  have 
other  special  arrangements.  They  usually  produce  com- 
paratively large  amounts  of  pollen,  which  is  very  dry 
and  powdery,  and  easily  blown  about  by  the  wind.  The 
stamens  often  hang  out  of  the  flower,  so  that  their  pollen 
is  easily  shaken  out  by  the  breeze.  Their  stigmas,  too, 
project  in  a  similar  manner,  and  are  often  large  and 
feathery,  so  that  they  present  a  large  surface  on  which 
to  catch  the  pollen.  A  comparison  of  such  insect- 
pollinated  flowers  as  the  bean,  lime,  and  wild  rose,  with 
such  wind-pollinated  flowers  as  those  of  grasses,  cereals, 
some  willows,  alders,  pines,  etc.,  will  make  these  differ- 
ences clear. 

Wind-pollinated  flowers  may,  just  as  insect-pol- 
linated flowers,  have  stamens  and  stigmas  in  the  same 
or  in  separate  flowers.  Many  of  the  ordinary  meadow 
grasses,  and  barley,  wheat,  and  other  cereals  are  examples 
of  the  former  group  ;  maize,  willows,  hazel-nut  and  pines 
of  the  latter.  In  the  maize  the  "  tassel "  at  the  top  of  the 
plant  consists  of  a  group  of  staminate  flowers  from  which 
the  pollen  is  readily  shaken  out  and  blown  about  by  the 
least  breeze.  The  beautiful  "  silk,"  which  protrudes  from 


148  NATURE  TEACHING 

the  top  of  every  young  cob,  is  a  bunch  of  stigmas,  which, 
being  widely  spread  out,  readily  catch  the  pollen  grains 
as  they  float  in  the  air. 

Fruits  and  Seeds. 

The  production  of  seeds  is  the  most  important 
object  in  the  life  of  most  plants,  because  in  their  natural 
condition  this  is  the  chief  method  by  which  they 
multiply.  When  the  flower  has  been  pollinated  and 
fertilised,  the  petals  and  other  non-essential  parts  often 
fade  and  wither  away,  their  use  being  over.  The  pistil 
develops  into  the  fruit  containing  the  seeds,  each  one 
of  which,  as  we  have  already  learnt,  contains  a  young 
plant,  the  embryo.  It  is  important  to  distinguish  clearly 
between  fruits  and  seeds.  Seeds  are  formed  from  the 
ovules.  During  their  ripening  certain  changes  take  place 
in  the  ovary  which  contains  them,  resulting  in  the  forma- 
tion of  the  fruit.  The  fruit,  therefore,  is  the  ripened 
ovary,  and  contains  the  seeds,  the  ripened  ovules. 

Fruits  are  very  variable  in  character,  and,  accord- 
ing to  their  nature,  they  are  often  classified  in  various 
ways.  Some  of  the  different  kinds  of  fruits  are  dis- 
tinguished by  the  names  in  common  use,  for  instance, 
berries,  nuts,  pods,  etc. 

When  the  plant  has  formed  its  seeds  it  is  most 
important  that  these  should  be  placed  in  such  positions 
that  they  may  germinate,  and  that  the  seedlings  may 
have  a  good  chance  of  success.  Amongst  other  things 
it  is  of  advantage  that  they  should  be  scattered  to  some 
distance,  for  if  they  were  merely  dropped  from  the  plant 
on  to  the  ground  beneath,  the  seedlings  would  be  so 


FLOWERS  AND  FRUITS  149 

crowded  together  that  only  a  very  few  would  live.  Many 
of  the  plants  which  are  troublesome  weeds  are  so  owing 
to  their  good  methods  of  seed  dispersal.  In  studying 
the  dispersal  of  seeds  the  uses  of  the  different  kinds  of 
seeds  and  fruits  will  be  seen. 

Dispersal  of  Fruits  and  Seeds. 

There  are  four  principal  methods  by  which  seeds 
are  distributed  : — (i)  wind;  (2)  water;  (3)  animals  ;  the 
seeds  being  carried  either  inside  or  outside  the  animal ; 
(4)  by  some  explosive  apparatus. 

Wind.  Many  seeds — for  instance,  those  of  the 
common  grasses — are  extremely  small  and  light,  so  that 
they  readily  float  in  the  air.  Some  large  seeds  are 
carried  about  in  a  similar  manner,  and  these  are  often 
provided  with  thin  appendages  of  various  kinds  known 
as  "  wings."  Good  examples  of  winged  seeds  are  those 
of  the  pines,  whilst  in  the  ash,  elm,  and  maples  the  whole 
fruit  has  a  big  wing  and  is  blown  about.  Other  wind- 
borne  fruits  and  seeds  are  provided  with  downy  or  silky 
hairs  which  enable  them  to  float;  for  instance,  thistle, 
dandelions,  lettuce,  willow-herbs,  etc. 

The  seeds  of  many  plants  lie  at  the  bottom  of  dry 
seed -cases  (often  open  only  at  the  top)  and  out  of  which 
it  looks  extremely  difficult  for  the  seeds  to  get  until  the 
seed-case  decays.  On  a  still  day  this  is  so,  and  no  seeds 
escape.  When,  however,  there  is  a  strong  wind  blowing, 
the  plants  are  shaken  about  and  the  seeds  often  thrown 
or  sprinkled  to  a  considerable  distance.  It  will  be  easily 
understood  that  this  is  preferable  to  having  the  openings 
at  the  bottom,  for  in  the  latter  case  the  seeds  would 


150  NATURE  TEACHING 

simply  fall  through  and  a  dense  growth  of  seedlings 
spring  up  immediately  around  the  parent  plant.  The 
poppy,  wild  hyacinth  or  bluebell,  and  foxglove,  afford  good 
examples.  The  seeds  in  such  seed-cases  which  are  open 
above  would  be  liable  to  be  damaged  by  rain,  and  we 
often  find  that  this  is  guarded  against.  Thus  in  some 
fruits  the  openings  are  very  small,  whilst  other  fruits 
only  open  in  dry  weather,  closing  again  when  it  is  wet. 

Water-borne  fruits.  The  fruit  of  the  coco-nut, 
with  its  tough  fibrous  covering,  is  able  to  float  long 
distances  without  damage.  The  coco-nut  palm  is  now 
found  on  almost  all  tropical  shores,  and  is  one  of  the  first 
plants  to  reach  new  coral  islands,  often  many  miles  from 
the  nearest  land.  The  seeds  or  fruits  of  several  South 
American  and  West  Indian  plants  have  been  found  on 
the  shores  of  Scotland,  Norway,  etc.,  having  travelled 
some  4000  miles,  by  the  aid  of  the  Gulf  Stream.  Those 
who  live  near  streams  and  rivers  should  watch  for  seeds 
and  fruits  carried  down  by  the  water.  Interesting 
examples  may  sometimes  be  seen;  for  instance,  the  float- 
ing portions  of  the  fruits  of  the  white  water-lily  enclosing 
the  seeds,  and  the  seeds  of  sedges  and  other  similar 
plants  which  grow  by  the  waterside. 

Animals.  Many  fruits  are  provided  with  hooks 
and  spines,  whereby  they  become  attached  to  the  coats 
of  passing  animals.  The  greater  number  of  the  fruits 
which  do  this  are  commonly  spoken  of  as  "  burrs." 
Amongst  examples  common  in  Great  Britain  are  the 
fruits  of  butter-burr,  cleavers,  wood-avens,  enchanter's 
nightshade,  and  the  wood-sanicle.  The  sight  of  these 
fruits  sticking  to  a  person  or  an  animal  who  has  pushed 


FLOWERS  AND  FRUITS  151 

his  way  through  the  plants  must  be  familiar  to  every 
one.  The  fruits  with  the  seeds  inside  them  may  be 
carried  some  considerable  distance,  but  sooner  or  later 
they  are  sure  to  be  brushed  off,  and  some  probably  fall 
in  places  suitable  for  their  growth,  and  thus  spread  the 
plant  from  place  to  place. 

The  fruits  mentioned  in  the  preceding  paragraph 
are  all  small,  dry  and  hard.  Animals  also  play  a  large 
part  in  the  distribution  of  quite  another  set  of  fruits, 
namely  those  which  are  commonly  known  as  succulent 
or  fleshy  fruits.  The  fleshy  portion  is  usually  the  wall 
of  the  fruit,  the  seeds — the  important  part  to  the  plant 
— being  generally  small  and  hard.  Animals  eat  these 
fruits  for  the  sake  of  the  fleshy  portion,  and  the 
small,  hard  seeds  pass  uninjured  through  their  bodies. 
Examples  of  such  fruits  are  numerous ;  mention  need 
only  be  made  here  of  strawberries,  raspberries,  the 
various  kinds  of  currants,  grapes,  and  elderberries. 
Apples  and  pears  are  fleshy  instead  of  being  pulpy,  but 
they  are  equally  pleasant  to  animals,  and  their  seeds 
are  similarly  small,  smooth  and  hard.  In  plums, 
damsons,  peaches  and  other  "stone  fruit,"  the  seed  is 
protected  by  the  hard  stone,  and  most  animals  eating 
the  fruit  leave  the  seed  untouched.  The  fruits  of  such 
plants  are  often  green,  inconspicuous,  and  unpleasantly 
flavoured  whilst  the  seeds  are  unripe,  but  after  they  are 
ripe  the  fruits  are  often  brightly  coloured,  easily  seen, 
and  sweet  to  the  taste.  In  all  these  cases  the  part  of 
the  fruit  of  importance  to  the  plant — the  seed — is  care- 
fully protected  from  injury,  and  the  plant  actually 
benefits  from  what  seems  at  first  sight  a  destructive 


152  NATURE  TEACHING 

proceeding,  namely,  an  animal  eating  its  fruit.  Many 
of  the  fruits  of  this  class  have  been  greatly  altered  in 
character  by  cultivation  and  selection  by  man,  who  has 
increased  the  pleasant  edible  portion,  even  to  the  sup- 
pression of  the  seeds ;  for  instance,  bananas,  pineapples, 
seedless  oranges,  seedless  grapes,  etc. 

The  mistletoe,  which  has  a  fleshy  berry  much 
eaten  by  birds,  has  an  interesting  method  of  seed 
dispersal.  Its  seeds  are  extremely  sticky,  and  when  a 
bird  eats  the  fruit  the  seeds  adhere  to  its  bill.  The  bird, 
sooner  or  later,  cleans  its  bill  by  rubbing  it  against  the 
bark  of  the  tree  on  which  it  has  been  feeding,  or  of  some 
other  tree  to  which  it  has  since  flown.  The  seeds  stick, 
and  after  germination  pierce  the  bark  and  so  establish 
themselves.  Mistletoe  once  introduced  into  an  orchard 
may  thus  spread  from  tree  to  tree  and  become  a  trouble- 
some pest. 

Explosive  fruits.  There  are  some  fruits  which  possess 
power  of  themselves  to  throw  their  seeds  to  some 
distance.  Sitting  on  a  hot  August  day  by  a  furze  bush 
we  may  often  here  a  crackling  sound,  caused  by  the  ripe 
pods  bursting  open,  when  the  two  halves  twist  up 
and  throw  out  the  seeds.  The  fruits  of  the  violet  when 
ripe  "flip"  out  the  seeds,  owing  to  the  sides  of  the 
seed-box  pressing  on  the  smooth  seeds,  so  that  they  are 
shot  out  just  as  we  can  flip  a  wet  apple-pip  between 
thumb  and  finger. 

The  garden  balsam  and  the  wild  oxalis  have  special 
kinds  of  fruits  which,  when  ripe,  throw  out  the  seeds  to 
some  considerable  distance. 


FLOWERS  AND  FRUITS  153 

Variation  in  Seedlings. 

As  a  general  rule  the  seeds  produced  by  plants 
which  have  been  fertilised  by  pollen  from  another  flower 
of  the  same  species,  that  is  to  say  cross-fertilised, 
yield  more  vigorous  plants  than  the  seeds  from  self- 
fertilised  flowers.  When  cross-fertilisation  takes  place 
between  two  plants  of  the  same  species,  but  possessing 
some  different  characters,  the.  resulting  plants  usually 
possess  some  of  the  characters  of  each  parent.  Thus  a 
plant  which  bears  white  flowers,  crossed  with  one  which 
bears  red  flowers,  usually  gives  seedlings  whose  flowers 
are,  in  various  ways,  marked  with  red  and  white.  These 
facts  are  made  use  of  in  the  production  of  new  varieties 
of  plants,  both  economic  and  ornamental.  A  plant, 
possessing  some  one  desirable  character,  is  crossed  with 
another  plant  of  the  same  species,  with  some  other 
desirable  character,  and  the  seedlings  examined  with 
care ;  those  showing  the  required  characters  in  the 
greatest  degree  are  selected,  and  the  others  rejected.  It 
must  be  remembered  that  only  closely  -  allied  plants 
(plants  of  the  same  species),  are  as  a  rule  capable  of  being 
crossed  with  one  another.  Thus  the  various  kinds  of 
peas,  evening  primroses,  orchids,  etc.,  can  be  crossed  with 
one  another,  but  you  cannot  cross  a  pea  with  an  orchid, 
or  an  orchid  with  an  evening  primrose. 

These  variations  in  plants  are  further  made  use  of 
when  it  is  desired  to  produce  a  plant  with  some  special 
character,  whether  it  be  the  shape  or  colour  of  the 
flower,  the  size  of  the  seed,  or  some  particular  feature  in 
the  fruit.  A  large  number  of  seedlings  are  raised  frorn 


154  NATURE  TEACHING 

a  plant  which  possesses  the  desired  character  to  a 
certain  degree.  Those  which  show  this  desired  char- 
acter to  the  greatest  degree  are  allowed  to  grow  and 
their  seed  saved.  The  seedlings  from  these  are  again 
rigidly  selected,  and  the  process  repeated,  season  after 
season,  until  plants  are  obtained,  the  seeds  of  which  we 
can  depend  on  to  give  a  large  number  of  seedlings  with 
the  particular  character  in  question. 

A  desirable  kind  of  plant,  whether  the  desired 
character  be  in  foliage,  flower,  seed  or  fruit,  may  be 
perpetuated  by  propagation  by  cuttings,  budding  or 
grafting.  The  variations  presented  by  seedlings  afford 
the  means  of  producing  new  kinds  of  plants  ;  propaga- 
tion by  cuttings  or  grafts  enables  us  to  reproduce  these, 
otherwise  variable,  plants  with  the  assurance  that  their 
characters  will  be  permanently  retained. 

PRACTICAL  WORK 

Examine  any  plants  which  can  be  obtained,  and 
clearly  make  out  the  relation  to  each  other  of  flower- 
bud,  flower,  fruit  and  seeds.  Notice  how  the  plant  for 
some  time  forms  no  flowers,  and  that,  later,  first  flower- 
buds  appear,  then  open  flowers,  and  finally  fruits  con- 
taining seeds. 

Parts  of  a  Flower. 

Examine  any  of  the  following  flowers  obtainable: — 
tulip,  lilies,  buttercups,  wild  rose,  evening  primrose,  pea, 
bean,  wallflower,  anemone,  dead  -  nettle,  primrose, 
geranium,  cucumber,  marrow,  hazel,  alder,  willows,  and 
pines.  Some  are  \n  flower  almost  the  whole  year 


FLOWERS  AND  FRUITS  155 

round.  Others  must  be  examined  as  occasion  offers. 
In  the  text  the  tulip,  lily,  evening  primrose,  etc.,  were 
suggested  because  they  are  large  and  their  parts  are 
easily  distinguishable,  but  many  of  the  others  will  serve 
almost  equally  well. 

In  all  cases  endeavour  to  distinguish  the  sepals, 
petals,  stamens  and  pistil.  Make  enlarged  drawings  of 
the  stamens  and  pistils,  and  show  the  parts  of  which 
they  are  composed,  and  the  stages  in  the  progress  of  the 
young  ovary  into  the  ripe  fruit. 

Note  carefully  those  plants  which  have  stamens  and 
pistil  in  the  same  flower,  and  those  which  have  them  in 
separate  flowers.  Examine  the  flowers  for  honey,  and 
make  a  list  of  all  the  flowers  found  which  contain  honey. 

Under  cultivation  the  stamens  of  many  plants  have 
lost  their  original  character,  and  have  become  converted 
into  petal-like  structures,  thus  giving  rise  to  what  are 
known  as  " double  flowers"  Many  of  these  flowers  form 
no  seeds,  owing  to  the  fact  that  they  have  lost  the  pollen- 
bearing  stamens,  which,  as  we  have  already  learnt,  are 
necessary  for  the  production  of  seed.  Many  varieties  of 
roses,  geranium,  balsams,  and  hollyhocks  furnish  good 
examples  for  examination. 

The  flowers  of  grasses  and  cereals  have  no  sepals 
and  petals  in  the  ordinary  sense  of  the  words.  They 
have  a  number  of  scaly  structures  instead,  but  their 
stamens  and  pistils  are,  as  a  rule,  easy  to  find.  Examine 
some  of  the  following : — wheat,  barley,  maize,  and  the 
common  meadow  grasses. 

Examine  the  "  flower  "  of  the  sunflower.  The  yellow 
structures  around  the  edge  are  very  different  from 


156  NATURE  TEACHING 

the  central  portion,  and  at  first  suggest  petals.  Where, 
then,  are  the  stamens,  and  the  pistil  ?  Cut  the  head 
through  :  the  middle  is  seen  to  be  made  up  of  a  number  of 
separate  tubular  bodies,  each  of  which  possesses  its  own 
petals,  stamens  and  pistil.  The  head  is  not  a  single  flower, 
but  a  collection  of  flowers.  This  is  true  of  all  the  plants  in 
the  large  order  to  which  the  sunflower  belongs,  including 
the  daisy,  groundsel,  pyrethrum,  Michaelmas  daisy,  etc. 

Experiments  in  Cross-fertilisation. 

Examine  the  separate  pistillate  and  staminate 
flowers  of  the  cucumber  or  vegetable  marrow,  and  learn 
how  to  distinguish  them  before  the  flower-buds  are 
open.  Watch  them,  and  notice  that  the  fruits  are  only 
formed  from  pistillate  flowers.  Staminate  flowers  die 
after  shedding  their  pollen. 

Tie  up  two  pistillate  flower-buds  (which  are  almost 
ready  to  open)  in  separate  bags  made  of  tough  paper  (for 
instance,  flat  sugar-bags),  with  a  string  put  through  them 
as  shown  in  Figs.  19  and  20.  When  one  of  these  flowers 
is  open,  pluck  a  staminate  flower  and  remove  its  petals  ; 
uncover  the  pistillate  flower,  and  gently  touch  its  stigma 
with  the  pollen-bearing  portion  of  the  staminate  flower, 
so  that  some  of  the  pollen  sticks.  Replace  the  bag. 
Leave  the  second  pistillate  flower  tied  up  the  whole 
time.  The  first  should  form  a  ripe  fruit,  the  second  not. 

Select  two  plants  of  the  same  kind,  but  possessing 
well-marked  differences ;  for  instance,  different-coloured 
polyanthus,  or  begonia.  Carefully  cut,  or  pull  off,  from  one 
flower  some  of  the  stamens  which  are  just  shedding 
their  pollen,  and  carry  them  to  the  flower  of  the  other 


FLOWERS  AND  FRUITS 


157 


plant  in  which  the  stigma  is  mature  (they  are  then  some- 
what sticky).  Touch  the  stigma  with  the  stamens,  so 
that  some  of  the  pollen  grains  adhere.  Tie  a  label  or 
mark  near  the  flower,  that  it  may  be  recognised  in  future, 
and  make  a  note  in  your  note-book  of  the  circumstances 
of  the  experiment.  Repeat  the  operation  with  several 
flowers.  When  the  fruit  is  ripe,  gather  it,  sow  the  seed, 
and,  later,  plant  out  the  young  seedlings  in  the  garden. 


FIG.  1 9. —  Bag  for 
pollination  experi- 
ments. (After 
Bailey.) 


FlG.    20.  —  Bag    for 
pollination   experi-  . 
ments,     tied    over 
flower.  (After 

Bailey.) 


When  the  plants  blossom  examine  their  flowers,  and 
notice  how  they  differ  from  each  other  and  from  the 
parent  plants.  A  similar  series  of  experiments  may  be 
carried  out  with  such  plants  as  coleus,  balsam,  tomato, 
sweet  peas,  etc. 

When  it  is  desired  to  effect  cross-fertilisation  with 
great  accuracy,  precautions  must  be  taken  to  prevent 
access  to  the  stigma  of  pollen  from  any  other  flower  than 
the  one  selected.  Thus  in  the  last  experiment  pollen 


158  NATURE  TEACHING 

might  also  have  been  naturally  brought  from  another 
flower  in  addition  to  that  from  the  one  actually  used. 
Choose  the  flower  to  receive  the  pollen  while  still  in  the 
bud-stage,  before  the  anthers  have  ripened  and  any 
pollen  has  escaped.  Gently  open  the  bud  and  remove 
the  stamens,  either  by  cutting  them  out  by  means  of 
fine-pointed  scissors,  or  by  pulling  off  their  heads  by 
means  of  forceps.  Protect  the  flower,  thus  prepared, 
from  insect  visits  by  covering  it  with  a  muslin  or  paper 
bag,  which  may  be  conveniently  fixed  over  a  small  branch 
having  upon  it  several  prepared  flowers.  After  a  few 
days  the  stigmas  will  be  mature  and  ready  to  receive 
the  pollen.  Then,  temporarily  remove  the  bags  and 
apply  pollen  from  a  selected  flower  to  the  stigmas.  Re- 
place the  bags  immediately,  and  leave  them  until  the 
flower  fades.  When  this  has  occurred,  remove  the  bags ; 
tie  a  label  near  to  the  ripening  fruit  in  order  that  it  may 
be  identified.  As  before,  raise  plants  from  the  seeds, 
and  compare  them  with  their  parents,  this  time  definitely 

known. 

Dispersal  of  Seeds. 

The  practical  work  on  this  subject  must  in  the  main 
consist  of  observations  made  out-of-doors.  Examine 
the  weeds  which  come  up  in  the  garden,  and  endeavour 
to  find  out  how  they  probably  got  there  ;  that  is  to  say, 
whether  their  seeds  are  likely  to  have  been  blown  by  the 
wind,  carried  by  birds  and  other  animals,  or  introduced 
in  other  ways. 

In  addition  to  the  weeds  of  the  garden,  the  plants 
growing  on  walls  and  in  the  hollows  of  trees — for  instance, 
in  the  crowns  of  pollarded  willows — should  be  noted,  and 


FLOWERS  AND  FRUITS  159 

their  fruits  and  seeds  examined  in  the  hope  of  determin- 
ing how  they  also  reached  these  out-of-the-way  places. 

It  is  not,  as  a  rule,  difficult  to  suggest  the  possible 
means  by  which  the  plants  have  reached  their  present 
situations,  if  attention  is  paid  to  the  previous  notes  on 
seed  dispersal,  and  if  a  careful  study  is  made  of  the 
examples  given  below. 

Wind-Borne  Seeds. 

Examine  the  seeds  of  ordinary  lawn  grass  and  see 
how  small  and  light  they  are,  and  that  they  are  readily 
blown  about  in  the  wind.  If  any  wild  orchids  are  to  be 
found  in  your  neighbourhood  examine  the  seeds  of  some 
of  these.  They  are  extremely  small  and  also  readily 
carried  in  the  air. 

Collect  dandelion  "flowers"  in  various  stages,  or 
better  still  keep  one  particular  "  flower  "  under  observa- 
tion, and  notice  the  changes  through  which  it  passes. 
At  first  it  appears  as  a  bud  ;  this  opens  into  the  dande- 
lion "  flower,"  or,  as  we  know  it  really  is,  collection  of 
flowers.  After  a  time  it  fades,  and  then  the  head  closes 
up,  and  might  at  first  sight  be  mistaken  for  a  bud. 
Open  another  head  in  a  similar  stage,  and  it  will  not  be 
difficult  to  see  that  the  lower  parts  of  the  old  withered 
flowers  are  swelling  and  forming  little  seed-like  bodies, 
In  another  few  days  the  head  once  more  opens,  but 
instead  of  the  flowers  we  find  a  large  number  of  small, 
dark  brown,  seed-like  bodies,  each  with  a  dainty  white 
parachute  attached  to  it.  Blow  these ;  they  float  away 
through  the  air  carrying  the  seed-like  bodies  with 
them,  and  after  travelling  a  longer  or  shorter  distance, 


160  NATURE  TEACHING 

according1  to  how  windy  it  is,  settle  down  on  the 
ground. 

Similar  observations  should  be  made  on  the  thistle, 
lettuce,  goafs-beard  or  salsify,  willow-herbs,  etc.  The 
details  will  vary  in  each  case,  but  all  are  alike  in  possess- 
ing some  means  of  enabling  their  seeds  to  be  readily 
blown  about  by  the  wind.  Additional  evidence  can  be 
obtained  by  going  on  a  dry  windy  day  in  summer  to  a 
piece  of  waste  ground  which  has  a  lot  of  thistles  growing 
on  it,  and  watching  the  thistle-down  blowing  about. 
Collect  some  pieces  of  thistle-down  and  note  the  small 
seeds  attached  to  them.  Then  recollect  that  each  little 
piece  of  thistle-down  is  probably  carrying  one  seed,  and 
you  will  understand  how  thistles  are  often  such  trouble- 
some pests  to  farmers,  and  why  it  is  so  important  that 
they  should  be  cut  down  before  and  not  after  they  have 
flowered. 

Take  a  ripe  pine-cone.  Pick  out  the  seeds  from 
-amongst  the  scales,  and  note  that  each  is  provided  with 
<a  thin  wing  or  sail. 

Examine  also  the  seeds  of  the  white  birch.  These 
•are  very  small,  and  each  is  provided  with  a  delicate  thin 
wing.  In  many  localities  near  London  and  elsewhere, 
numerous  instances  will  be  seen  of  young  birches  coming 
up  on  waste  lands,  a  result  due  very  largely  to  their 
effective  method  of  seed  dispersal. 

Examine  ripe  fruits  of  the  maple  and  ash  "  keys." 
Both  of  these  have  wings  by  which  they  are  blown  about 
by  the  wind.  Cut  some  open  and  see  the  seeds  inside. 
In  the  pine  and  birch  the  seed  itself  had  a  wing,  whilst 
in  the  maple  and  ash,  it  is  the  fruit  which  is  vyinged, 


FLOWERS  AND  FRUITS  161 

the  seeds  inside  having  no  wings.  The  result  is  the 
same,  the  seeds  in  all  being  blown  about.  Make  sketches 
of  all  the  winged  seeds  or  fruits  examined. 

Look  at  a  ripe  poppy  fruit,  whilst  still  attached  to 
the  plant.  Around  the  top  edge  are  a  number  of  small 
holes,  through  which  it  is  apparently  impossible  for  the 
seeds  to  get  out,  until  the  fruit  drops  off  or  decays. 

Place  a  sheet  of  newspaper  under  the  plant,  and  then 
pull  the  head  to  one  side  and  let  it  spring  back  with  a 
jerk.  Some  of  the  seeds  will  probably  be  thrown  out 
through  the  little  holes,  and  will  be  found  on  the  paper. 
On  a  windy  day  this  process  goes  on  naturally,  and  the 
holes  being  placed  at  the  top  ensures  that  seeds  are  only 
set  free  when  the  conditions  are  such  that  they  will  be 
scattered  to  some  distance  from  the  parent  plant. 

Similar  observations  can  be  made  on  the  fruits  of 
the  wild  hyacinth,  bluebell,  etc.  Notice  how  in  all  of 
these  plants  the  seed-cases  are  placed  on  the  top  of  long, 
springy  stalks. 

Dispersal  by   Water. 

Examine  fruits  of  water-lilies,  sedges,  and  other 
plants  found  naturally  growing  by  the  waterside,  and 
see  if  any  of  them  are  able  to  float  in  water.  Collect  all 
seeds  and  fruits  found  floating  on  streams  or  ponds  and 
endeavour  to  ascertain  to  what  plants  they  belong. 

Dispersal  by  Animals. 

Collect  in  the  hedge-row  a  spray  of  goose-grass  or 
cleavers  which  has  a  number  of  the  little  round  green  or 
brown  fruits  on  it.  Pull  the  spray  along  your  coat  and 

L 


162  NATURE  TEACHING 

notice  how  the  fruits  stick  to  the  cloth.  Make  similar 
simple  experiments  with  fruiting  sprays  of  the  hemp- 
agrimony,  burdock,  enchanter's  nightshade,  wood-sanicle 
or  avens,  if  any  of  these  are  obtainable.  Examine  the 
little  bodies  which  stick  to  your  coat  in  each  case,  and 
satisfy  yourself  that  they  are  really  the  fruits  of  the 
plant,  and  that  they  do  contain  the  seeds. 

Dogs  which  have  been  running  through  copses,  or 
"  grubbing  about "  in  a  hedge,  will  often  be  found  to 
have  a  large  number  of  various  fruits  sticking  to  them. 
If  occasion  offers,  look  these  over  and  try  and  find  out 
to  what  plants  they  belong. 

Make  careful  drawings  of  all  the  fruits  examined, 
showing  the  hooks  on  each. 

Examine  the  following  fruits : — strawberry,  black- 
berry, raspberry,  currants  and  grape.  Notice  that  these 
all  consist  of  a  pulpy  portion,  pleasant  to  eat,  and 
contain  small,  hard  pips  (seeds).  Make  drawings  of  all 
of  these. 

Cut  an  apple  across  and  also  lengthways,  and  make 
a  drawing  to  show  the  position  of  the  seeds. 

Similarly  make  sketches  to  show  the  structure  of  a 
plum  or  other  stone  fruit.  Crack  the  stone  and  observe 
the  seed  inside.  Show  on  your  drawing  the  great 
thickness  of  the  stone. 

Dispersal  by  Explosive  Action. 

Watch  a  furze  bush  on  a  hot  day  in  late  summer  and 
try  and  detect  some  of  the  pods  opening  and  scattering 
their  seeds.  Squeeze  some  ripe  black  pods  at  their  ends, 
and  notice  how  they  split  and  twist  up,  throwing  out 


FLOWERS  AND  FRUITS  163 

the  seeds.  Try  the  same  experiment  with  pods  of 
vetches,  lupines,  and  similar  plants. 

Get  some  plants  of  wood  sorrel  (oxalis),  and  balsams, 
with  ripe  fruits  on  them.  Slightly  squeeze  the  fruits  and 
notice  how  they  curl  up,  and  shoot  out  the  seeds.  By 
placing  a  sheet  of  paper  under  the  plant,  find  out  how 
far  the  seeds  are  thrown. 

Make  similar  observations  on  the  violet.  Sketch 
the  fruits  of  all  these  plants  before  and  after  they  have 
opened,  and  try  and  understand  what  really  goes  on  in 
each  case. 


CHAPTER  VIII 

WEEDS 

IN  all  gardening  and  agricultural  operations  the  careful 
cultivator  makes  it  his  constant  care  to  destroy  weeds. 
These  are  wild  plants  which  invade  the  cultivated  land 
and  impede  the  growth  of  the  crop.  Weeds  act  injuri- 
ously in  several  ways.  They  crowd  out  cultivated  crops 
by  their  leaves  overshadowing  and  robbing  the  crop  of 
the  necessary  sunlight,  which  as  we  have  seen,  plants 
make  efforts  to  secure,  being  essential  to  their  growth. 
The  roots  of  the  weeds  rob  the  soil  of  moisture,  thus 
retarding  the  crop's  growth.  At  the  same  time  the 
weeds  use  up  some  of  the  available  plant  food,  thus 
leaving  the  crop  insufficiently  fed.  This  is  particularly 
the  case  with  the  nitrogen,  as  when  there  are  many 
weeds  in  the  soil  their  roots  compete  with  those  of  the 
crop  in  taking  up  the  nitrates  as  fast  as  they  are  formed 
in  the  soil,  and  thus  the  crop  may  be  unable  to  secure  a 
sufficient  supply  for  the  purposes  of  vigorous  growth. 

When  a  piece  of  land  is  newly  brought  under  culti- 
vation much  trouble  is  often  experienced  in  removing 
the  weeds,  which  grow  from  the  seeds  lying  dormant  in 
the  soil,  and  from  others  brought  there  by  the  wind,  or 

164 


WEEDS  165 

other  agents  in  seed  dispersal.  Even  after  years  of 
cultivation,  weeds  continue  to  make  their  appearance, 
owing  to  the  great  distances  to  which  the  seeds  of  many 
plants  can  travel.  The  seeds  of  weeds,  moreover,  are 
often  introduced  in  stable  and  farmyard  manures,  and 
compost.  For  this  reason,  it  is  desirable  that  manures 
of  this  description  should  be  well  rotted  before  being 
used. 

In  getting  rid  of  weeds  it  is  very  important  to 
remove  them  before  they  have  had  an  opportunity  of 
ripening  their  seeds.  If  this  precaution  is  not  taken  the 
cultivator  will  never  have  his  land  clean,  and  will  be 
subject  to  unending  trouble  and  expense.  Many  weeds 
propagate  themselves  by  suckers  and  rooting  branches ; 
as,  for  example,  couch  grass  or  twitch,  coltsfoot,  dande- 
lions. It  is  essential  that  these  should  be  completely 
dug  up  and  destroyed  ;  merely  chopping  them  with  a 
hoe  or  spade  only  helps  in  spreading  them,  and  thus  to 
cause  future  trouble. 

The  kinds  of  weeds  which  make  their  appearance 
in  any  particular  place  often  indicate  very  clearly  the 
character  of  the  soil.  Such  knowledge  may  be  of  con- 
siderable use  to  the  cultivator,  for  he  may  often  thus,  at 
a  glance,  learn  facts  of  great  value  concerning  certain 
areas. 

The  traveller's  joy  or  old  man's  beard  (Clematis], 
fumitory,  rock  rose,  and  salad  burnet  are  almost  entirely 
confined  to  chalky  or  limestone  soils,  and  the  beech, 
yew,  box  and  wild  guelder  rose  are  often  characteristic. 
Sandy  localities  are  often  easily  distinguishable  by  the 
presence  of  heaths,  furze,  broom,  whortleberry,  Spanish 


166  NATURE  TEACHING 

chestnut,  and  birch  trees,  and  by  such  less  conspicuous 
plants  as  the  small  lady's  mantle,  corn  spurrey,  etc. 
The  presence  of  the  lesser  celandine  or  pilewort  is  almost 
certain  proof  of  the  presence  of  clay.  Wheat  and  mari- 
golds are  characteristic  crops,  and  oak  trees  thrive  well 
on  clayey  soils.  Wet  lands  are  sufficiently  indicated 
by  the  growth  of  rushes,  sedges,  and  other  moisture- 
loving  plants. 

PRACTICAL  WORK 

Examine  the  plants  which  occur  in  the  garden,  and 
endeavour  to  determine  where  they  come  from,  and  how 
it  is  that  some  of  them  appear  again  and  again  after  all 
attempts  to  get  rid  of  them.  In  many,  this  will  be  found 
to  be  due  to  a  good  method  of  seed  dispersal.  Others, 
which  are  exceedingly  difficult  to  get  rid  of,  have  under- 
ground stems,  bulbs,  and  tubers,  which  remain  in  the 
ground. 

Make  lists  of  the  plants  found  on  some  piece  of  waste 
ground,  or  which  come  up  as  weeds  in  the  garden,  and 
endeavour  to  understand  how  each  spreads  from  place 
to  place,  whether  by  its  seeds  or  by  underground  stems 
and  roots. 

Preserving  Plant  Specimens. 

Collect  specimens  of  every  weed  found  in  the 
school  garden,  and  preserve  them  for  future  examination 
and  reference.  This  may,  with  most  plants,  easily  be 
done  by  carrying  out  the  following  simple  directions. 
The  first  requisite  is  drying  material,  which  is  best  of 
coarse,  stout,  and  unsized  paper.  Ordinary  blotting- 
paper  is  much  too  tender  except  for  very  delicate  plants. 


WEEDS  167 

If  nothing  better  is  available,  newspaper  answers  fairly 
well.  Cut  the  paper  into  single  sheets  of  convenient  size 
(about  1 6  by  12  inches  is  recommended).  Next  obtain 
two  boards,  about  half  an  inch  thick,  and  slightly  larger 
than  the  sheets  of  drying-paper.  A  few  stones  or  bricks 
(best  wrapped  in  stout  brown  paper)  will  complete  the 
plant-drying  outfit. 

In  gathering  a  plant,  take  care  to  get  as  complete 
a  specimen  as  possible.  A  perfect  botanical  specimen 
should  show  root,  stem,  leaves,  flowers,  and  fruit  Some 
plants  are  too  large  to  allow  of  this,  and  in  their  case 
portions  should  be  selected  to  make  the  dried  specimen 
as  fully  representative  of  the  plant  as  possible. 

Take  one  of  the  boards,  and  put  on  it  two  or  more 
sheets  of  the  drying-paper.  On  the  top  sheet  lay  the 
plant,  carefully  arranging  it  so  that  its  parts  are  as  nearly 
as  possible  in  their  natural  positions.  On  the  plant  place 
some  more  sheets  of  drying-paper,  and  then  arrange 
another  plant.  (Two  plants  must  never  be  placed  on 
top  of  one  another  between  the  same  two  pieces  of  paper.) 
Go  on  in  this  way  until  all  the  plants  are  spread  out,  and 
finally  put  on  the  second  board,  and  the  weights. 

By  the  next  day  the  sheets  of  paper  will  probably 
have  become  damp,  and  must  be  changed  for  dry  ones. 
Damp  papers  should  be  dried  in  the  sun.  When  chang- 
ing the  plants,  lift  them  carefully  and  take  care  that  their 
leaves,  etc.,  are  in  natural  positions.  The  work  of  arrang- 
ing the  parts  in  position  is  often  best  accomplished  after 
drying  has  gone  on  for  a  few  hours.  The  plant  is  then 
limp,  and  the  leaves,  etc.,  will  be  found  to  remain  in  any 
position.  When  quite  dry  any  attempt  to  move  a  part 


168  NATURE  TEACHING 

usually  results  in  breaking  it.  With  good  absorbent 
paper,  used  perfectly  dry,  two  changes  are  often  sufficient, 
except  for  thick-leaved  plants,  which  require  more. 

For  future  reference  it  is  advisable  to  mount  the 
dried  plants  on  sheets  of  paper.  The  same  size  should 
be  used  throughout  (16  inches  by  io£  inches  is  a  common 
and  convenient  size),  and  only  one  species  of  plant  should 
be  placed  on  any  one  sheet.  Fix  the  plants  to  the 
sheets  by  small  strips  of  gummed  paper. 

Write  on  each  mounted  sheet  the  name  of  the 
plant  in  the  bottom  left-hand  corner,  and  add  locality 
and  date  of  collection,  time  of  flowering,  nature  of  soil  in 
which  it  grows,  whether  it  is  a  troublesome  weed  or  not, 
and  any  other  facts  of  interest.  These  observations 
should  be  made  at  the  time  the  plant  is  collected  and 
written  on  a  slip  of  paper,  which  should  be  put  with  the 
plant  when  drying,  and  then  neatly  copied  on  the  sheet 
on  which  the  specimen  is  mounted.  Plants  collected, 
dried  and  mounted  without  notes  made  at  the  time  of 
collection,  giving  some  or  all  of  the  particulars  above, 
lose  much  of  their  value. 

A  collection  of  this  kind  may  be  made  by  individual 
pupils,  but  it  will  usually  be  found  advisable  to  make  a 
general  collection  for  the  school.  The  work  of  drying 
arid  mounting  can  then  be  distributed  amongst  a  number, 
and  a  collection  formed  which  will  steadily  grow  and 
become  of  permanent  value  and  increasing  interest. 


CHAPTER   IX 

ANIMAL   PESTS   OF   PLANTS 

CONSTANT  disappointment  and  annoyance  are  caused 
to  the  cultivator  by  the  ravages  of  insects  and  other 
animals  which  devour  or  otherwise  injure  his  crops,  so 
that  in  his  attempt  to  raise  any  crop  the  pupil  is  sure  to 
have  the  presence  of  some  animal  pests  and  their  habits 
unpleasantly  brought  to  his  notice.  Caterpillars  are 
certain  to  be  amongst  the  first  thus  found,  and,  as  an 
example  of  an  insect's  life-history,  we  may  shortly 
summarise  what  can  be  observed  in  their  case. 

Life- History  of  a  Caterpillar. 

A  caterpillar  is  produced  direct  from  the  egg  laid 
by  the  parent.  It  will  be  found  to  be  a  soft-bodied 
insect,  with  a  head,  and  a  long  body  divided  into 
"  segments"  Behind  the  head,  on  each  of  the  first  three 
segments,  is  one  pair  of  short-jointed  legs.  On  some  of 
the  remaining  segments  and  on  the  last  will  be  found 
soft  "  sucker-feet "  (or  "pro-legs  "),  but  never  more  than 
five  pairs  in  all.  The  head  is  hard,  and  provided  with 
very  small  eyes  and  strong  hard  jaws.  The  caterpillar 
lives  for  some  time,  eating  voraciously  and  casting  its 

169 


170  NATURE  TEACHING 

skin  periodically  to  allow  for  growth  in  size.  When  it  is 
full  grown  and  contains  a  large  amount  of  fat,  it  again 
sheds  its  skin  and  appears  as  the  "  chrysalis  "  or  "pupa." 

This  stage  is  comparatively  short  and  is  a  period 
of  rest,  when  the  body  of  the  perfect  insect  is  built 
up  anew  from  the  body  of  the  caterpillar.  At  its  close, 
the  hard  skin  cracks,  and  the  fully  developed  moth  or 
butterfly  comes  out. 

The  perfect  insect  has  two  pairs  of  large  wings 
clothed  with  scales,  three  pairs  of  long-jointed  legs, 
large  eyes,  and,  in  place  of  the  jaws  of  the  caterpillar, 
a  long  tubular  proboscis  which  serves  to  suck  up  the 
honey  which  may  form  its  food.  The  female  moth  or 
butterfly  then  seeks  the  right  food-plant  and  deposits  a 
varying  number  of  eggs,  from  which  the  caterpillars 
hatch.  The  eggs  may  be  laid  singly  or  in  clusters,  and 
are  of  very  varied  appearance.  The  caterpillars  that 
hatch  therefrom  are  also  very  varied  in  colour,  being 
white,  green,  or  marked  with  red,  black  and  yellow ; 
some  are  perfectly  smooth,  whilst  others  are  covered 
with  hairs,  spines  or  bristles.  Some  caterpillars  are 
very  small — for  instance,  those  found  in  "  maggotty " 
peas — whilst  others  are  as  much  as  four  inches  long — for 
example,  the  caterpillars  of  the  goat's-moth,  and  of  the 
death's-head  moth.  The  resting  or  pupal  stage  is  often 
spent  on  the  food-plant,  sometimes  in  a  cocoon ;  but 
many  chrysalides  are  found  in  the  earth. 

Crops  are  destroyed  only  by  the  caterpillar.  Neither 
the  pupa  nor  the  perfect  insect  injure  plants,  and,  as  has 
already  been  stated,  moths  and  butterflies  are  important 
agents  in  the  pollination  of  many  flowers. 


ANIMAL  PESTS  OF  PLANTS  171 

Life- History  of  a  Beetle. 

Many  destructive  agricultural  pests  belong  to  another 
order  of  insects,  the  beetles.  These  go  through  a  similar 
series  of  changes:  egg,  larva  (called  " grub"  m  this 
order),  chrysalis  or  pupa  up  to  the  perfect  insect.  The 
larvae  of  beetles  are  often  provided  with  three  pairs  of 
jointed  legs,  but  have  no  sucker-feet.  Sometimes  they 
are  entirely  without  legs,  and  are  then  usually  white  and 
fleshy.  They  have  very  strong  biting  jaws,  and  the 
segments  of  the  body  are  not  so  well  marked  as  in 
caterpillars. 

The  pupae  are  inactive,  often  enclosed  in  a  cocoon, 
and  in  them  the  form  of  the  forthcoming  beetle  is  easily 
recognised. 

The  perfect  insect  is  usually  hard,  with  two  pairs 
of  wings,  of  which  the  first  pair  are  hard  and  long, 
forming  a  sheath  for  the  second  pair,  which  are  thin  and 
membranous.  Their  jaws  are  usually  strong  and  well 
adapted  to  biting. 

Beetles  thus  prove  destructive  both  in  the  larval 
and  in  the  mature  stage ;  they  feed  upon  a  great  variety 
of  substances.  Some,  like  the  grubs  of  the  flea-beetles, 
burrow  in  the  leaves  of  plants ;  others  eat  the  roots 
underground — for  instance,  wire-worms,  the  grubs  of 
cockchafers,  and  of  daddy  longlegs  or  "  leather  jackets." 
The  death-watch  beetle  bores  into  beams  in  houses,  and 
several  others  eat  their  way  into  the  stems  of  trees  ;  and 
the  ravages  of  a  little  beetle,  the  so-called  "furniture 
worm,"  in  furniture  are  well  known.  Biscuits,  grain,  and 
other  stored  food-stuffs,  are  very  liable  to  the  attack  of 


172  NATURE  TEACHING 

small  beetles  called  weevils,  and  others  have  a  liking 
even  for  cigars  and  cigarettes. 

Green  Fly. 

Every  gardener  is  sure  at  some  time  or  other  to 
have  his  attention  called  to  another  group  of  insects, 
"green  fly,"  or  plant  lice.  These  are  often  found  on 
young  shoots  and  buds,  and  if  nothing  is  done  to  check 
them  they  increase  enormously,  and  the  leaves  on  which 
they  are  often  curl  up,  wither,  and  die.  Green  fly  are 
provided  with  a  beak  or  proboscis,  which  they  thrust  into 
the  plant  and  use  to  suck  up  its  juices.  Each  green  fly 
is  very  small,  but  they  often  occur  in  such  countless 
numbers  that  together  they  do  a  great  deal  of  harm 
to  the  plant.  Although  usually  called  green  fly  some 
are  black  ;  for  instance,  the  plant  lice  often  found  on 
beans. 

The  presence  of  green  fly  is  often  indicated  by  a 
sticky  deposit  on  the  leaves  of  the  plants,  which  some- 
time trickles  down  the  stems  or  drops  on  the  ground. 
This  sticky  liquid  is  called  "  honey  dew,"  and  is  produced 
by  the  green  fly.  In  London  the  lime  trees  are  often 
attacked  by  green  fly,  and  the  honey  dew  dropped  by 
them  forms  damp  patches  on  the  pavement,  so  that 
walking  along  and  watching  the  pavement  you  can 
often  tell  that  you  are  passing  under  a  lime  tree  and 
that  the  tree  is  attacked  by  green  fly. 

Rose-growers  are  often  troubled  by  finding  the 
leaves  of  their  plants  disfigured  by  having  pieces  cut  out 
of  them  as  neatly  as  if  done  by  a  sharp  knife.  The 
offenders  are  certain  biting  bees  which  cut  out  these 


ANIMAL  PESTS  OF  PLANTS  173 

pieces  and  use  them  to  build  nests  in  holes  in  trees  and 

similar  places. 

Flies. 

Distinguished  from  the  insects  already  mentioned, 
all  of  which  have  four  wings  (some  green  fly  have  no 
wings),  are  the  flies  which  only  possess  two.  The 
larvae,  usually  called  maggots,  are  footless  grubs  with  an 
undefined  head  ;  they  are  thus  distinguishable  from  the 
grubs  of  beetles.  The  pupae  are  inactive  and  often 
resemble  brown  seeds.  The  adult  insects  have  two 
membranous  wings,  and  the  mouth  is  formed  for  suction 
and  not  for  biting. 

The  grubs  of  some  flies  burrow  in  leaves,  and  eat 
out  tunnels  in  the  soft  tissue.  Thus  cineraria  leaves  are 
often  disfigured  by  meandering  trails  made  by  the  grubs 
of  the  leaf-miner,  and  the  grubs  of  the  celery-fly  are 
responsible  for  the  blister-like  patches  often  seen  on 
celery  leaves ;  in  these  cases  the  green  tissue  of  the  leaf 
is  eaten,  leaving  the  colourless  upper  and  lower  skin. 
The  grubs  or  maggots  can  often  be  seen  in  these 
blisters,  and  here  they  change  into  the  pupal  or  resting 
condition,  whence  later  the  perfect  winged  fly  emerges. 

Slugs  and  Snails. 

Slugs  and  snails  also  cause  a  great  deal  of  damage 
in  gardens.  They  are  obviously  very  different  from  the 
pests  already  noticed,  and  belong  to  another  class  of 
animals  altogether,  the  Molluscs,  or  Shellfish.  In  the 
ordinary  garden  snail  the  shell  is  easily  seen,  but  in 
most  slugs  there  is  no  visible  shell,  it  being  present  only 
as  a  small,  hard  plate  embedded  in  the  flesh  of  the 


174  NATURE  TEACHING 

animal.  Snails  and  slugs  lay  eggs  in  damp  places,  on 
leaves  of  plants,  etc.,  and  from  these  hatch  directly  young 
snails  or  slugs,  there  being  in  this  group  no  stages  cor- 
responding to  the  larvae  or  pupae  of  insects. 

Most  snails  and  slugs  feed  on  vegetable  matter,  and 
their  ravages  in  gardens  are  familiar  to  every  one.  The 
garden  snail  and  the  ordinary  grey  slug  are  to  be  found 
in  almost  every  garden,  and  in  fields  the  large  black  slug 

is  often  met  with. 

Remedies. 

In  order  to  limit  the  damage  done  to  crops  by 
injurious  insects,  various  steps  may  be  taken  ;  first  of  all 
the  eggs  of  butterflies  and  moths  when  seen  upon  leaves 
should  be  destroyed,  and  the  caterpillars  should  be 
picked  off  and  killed.  When  these  remedies  are 
inapplicable  .various  insecticides  may  be  dusted  or 
sprayed  upon  the  plants  attacked.  Full  directions  con- 
cerning the  use  of  many  of  these  are  to  be  found  in  the 
excellent  leaflets  of  the  Board  of  Agriculture,  obtainable, 
free  of  charge,  on  application  to  the  Secretary,  4  White- 
hall Place,  S.W. 

Many  caterpillars  are  kept  in  check  by  being 
attacked  by  other  insects  which  lay  their  eggs  in  their 
bodies.  The  insects  attacked  are  not  immediately 
killed  by  this  operation,  which  commonly  takes  place 
in  the  caterpillar  stage,  but  the  caterpillars  often  live 
and  pass  into  the  chrysalis  stage.  .  By  this  time  the 
larvae  of  the  insect  which  has  attacked  them  have 
hatched  out  and  usually  kill  their  host  by  feeding  on  it 
in  this  stage,  so  that  instead  of  the  expected  moth  or 
butterfly  issuing  from  the  chrysalis,  a  number  of  flying 


ANIMAL  PESTS  OF  PLANTS  175 

insects,  the  mature  form  of  the  attacking  insect,  make 
their  appearance.  Not  only  caterpillars,  but  all  kinds  of 
destructive  insects  may  be  thus  destroyed  by  other 
insects,  and  many  species  that  would  otherwise  become 
very  injurious  are  thus  kept  in  check. 

Slugs  and  snails  are  best  kept  in  check  by  hand 
picking,  or  by  trapping  them  with  cabbage  leaves. 

PRACTICAL  WORK 

Collect  a  few  caterpillars,  together  with  portions 
of  the  plant  on  which  they  are  feeding.  Place  these  in 
a  box,  in  the  bottom  of  which  is  a  little  garden-mould, 
to  the  depth  of  about  ij  inches.  Cover  the  box  with 
muslin,  perforated  zinc,  or  glass,  in  such  a  manner  that 
the  caterpillars  cannot  escape.  Supply  them  with  food 
morning  and  evening.  When  the  caterpillar  changes 
into  a  chrysalis,  note  where  the  chrysalis  places  itself, 
whether  it  is  buried  in  the  soil  or  whether  it  attaches 
itself  to  the  leaves  of  its  food-plant,  and  note  any  other 
arrangement  which  it  makes  for  its  protection.  Keep 
the  box  with  the  chrysalides  in  a  safe  place  until  the 
moths  or  butterflies  appear.  Make  notes,  with  sketches 
of  the  size,  colour,  and  appearance  of  the  insect  in  the 
various  stages.  Keep  an  account  of  the  time  occupied 
by  each  stage.  Record  the  plant  on  which  the  insect 
under  observation  is  found  feeding.  As  many  insects 
as  possible  should  be  raised  under  observation. 

Make  a  list,  which  may  be  added  to  from  time  to 
time,  of  the  insects  found  upon  particular  crops,  keeping 
specimens  of  the  insects,  drawings  or  descriptions,  with 
notes  of  the  parts  of  the  plants  attacked  and  of  the 


176  NATURE  TEACHING 

injuries  caused.  Thus  lists  may  be  made  of  insects 
found  upon  cabbages,  turnips,  corn,  lettuce,  peas,  beans, 
roses,  celery,  etc. ;  these  lists  may  prove  of  considerable 
interest  and  value.  In  preparing  these  lists,  efforts 
should  be  made  to  observe  the  habits  of  the  insect  and 
to  obtain  all  the  stages  from  the  egg  to  the  mature 
insect 

Collect  specimens  of  the  snails  and  slugs  found  in 
the  garden.  Observe  the  shell  in  snails,  and  note  how  the 
animals  withdraw  into  it  when  touched  or  alarmed  in  any 
way.  Compare  with  slugs  in  which  the  shell  is  appar- 
ently absent.  Put  snails  and  slugs  to  walk  on  a  piece 
of  glass,  and  looking  at  them  from  beneath  observe 
the  wave-like  contraction  of  the  muscles.  Notice  their 
eyes,  their  method  of  feeding.  Keep  some  for  a  time 
in  a  box,  and  supply  them  with  leaves ;  they  may  lay 
eggs,  and  if  so  watch  the  development  of  the  young 
animals. 

Insects  required  as  specimens  are  best  killed  by 
putting  them  into  a  "killing-bottle."  This  is  a  wide- 
mouthed  stoppered  bottle  in  which  some  fragments  of 
cyanide  of  potassium  have  been  placed,  and  some  plaster 
of  Paris,  mixed  with  water  to  the  consistency  of  thick 
cream,  poured  over  the  cyanide  so  as  to  cover  it  com- 
pletely. When  the  plaster  has  set,  the  bottle  is  ready  for 
use,  and  any  insect  placed  in  it  is  quickly  killed.  Owing 
to  the  extremely  poisonous  nature  of  potassium  cyanide, 
it  is  desirable  that  these  killing-bottles  should  be 
purchased  ready  for  use.  When  the  bottles  are  old  and 
exhausted,  care  should  be  taken  in  disposing  of  them,  so 
as  to  avoid  injury  to  persons  or  animals  by  any  remain- 


ANIMAL  PESTS  OF  PLANTS  177 

ing  cyanide.     //  is  impossible  to  be  too  careful  in  this 
respect. 

Remedies. 

Two  very  generally  useful  mixtures  for  spraying 
plants  with  are  : — 

Kerosene  or  paraffin  emulsion,  made  by  dissolv- 
ing half  a  pound  of  hard  soap  in  one  gallon  of  boiling 
water.  When  dissolved,  add  two  gallons  of  kerosene 
(paraffin)  to  the  hot  liquid,  and  immediately  churn  up 
well  with  a  syringe  until  the  mixture  becomes  creamy. 
This  is  the  stock  solution,  and,  before  using,  water 
should  be  added  to  make  it  up  to  thirty-three  gallons. 
Only  rain-water  or  other  soft  water  (that  is  without  lime) 
must  be  used. 

Whale-oil  soap.  Dissolve  one  pound  of  the  soap  in 
one  or  two  gallons  of  warm  water,  and  use  when  cold. 


M 


GLOSSARY 

Acid  (Latin,  acidus,  sour).  The  name  given  to  a  large  series  of 
substances,  which  possess,  amongst  other  properties,  (i)  a  sharp 
taste,  (2)  the  power  to  turn  moist  blue  litmus-paper  red,  and 
(3)  to  cause  carbonates  (such  as  lime  or  soda)  to  bubble  up  and 
give  -off  carbon  dioxide.  Vinegar  is  an  example  of  an  acid. 

Albumen  (the  Latin  word  for  the  white  of  an  egg).  Used  botanically 
for  a  reserve  of  plant  food  contained  in  the  seed.  See  foot- 
note, page  5. 

Alkaline  (Arabic,  al,  the  ;  kali,  ashes  of  a  plant,  "  glass-wort "). 
The  opposites  of  acids  ;  substances  which  turn  moist  red  litmus- 
paper  blue,  and  have  as  a  rule  a  peculiar  burning  taste. 
Slaked  lime  and  caustic  potash  are  common  examples. 

Analysis  (Greek,  analusis,  a  loosing  or  breaking-up).  The  separation 
of  a  substance  into  the  various  parts  of  which  it  is  composed. 

Apex  (the  Latin  for  summit).  The  growing  point  of  a  stem  or  root 
and  the  free  end  of  a  leaf. 

Assimilation  (Latin,  assimulatio,  a  making  like).  Used  to  denote 
the  process  by  which  the  raw  food  of  a  plant  is  changed  into 
plant  substance.  The  term  is  often  confined  to  the  formation 
of  starch  and  other  substances  from  water  and  carbon  dioxide 
in  sunlight  by  plants  containing  chlorophyll. 

Bacteria  (Greek,  bakterion,  a  small  stick  or  staff).  Minute  forms 
of  plant  life,  commonly  spoken  of  as  germs  and  microbes. 
The  decay  of  animal  and  vegetable  matters  is  largely  brought 
about  by  bacteria. 

Berry  (Latin,  bacca,  a  berry).  A  fruit  consisting  of  a  thin  outer 
skin,  and  a  pulpy  interior  in  which  the  seeds  are  embedded  ; 
e.g.  a  tomato. 

Botany  (Greek,  botanc,  grass,  or  more  generally  any  plant).  The 
study  of  plants. 

179 


180  GLOSSARY 

Bulb   (Latin,  bulbus,  a  bulb,  or  round  root).     Usually  an  under- 
ground leaf-bud,  containing  reserves  of  plant  food  stored  up  in 
thickened  leaves,  and  protected  on  the  outside  by  scale  leaves. 
Capillary  (Latin,  capillus,  a  hair).     Hence  any  very  fine  threads, 

tubes  or  cavities. 
Carbon  (Latin,  carbo,  a  cinder).     The  substance  which  forms  a 

large  proportion  of  all  organic  matter. 

Cereals  (Latin,  Ceres,  the  goddess  of  corn).     A  general  name  for 
those  grasses  whose  seeds  are  used  as  food,  e.g.,  maize,  rice, 
and  Guinea  corn. 
Chemical  (Arabic,  Kimia,  the  hidden  art  or  science).     The  science 

which  deals  with  the  composition  of  matter. 
Chlorophyll  (Greek,  chloros,  pale  green  or  grass-green  ;  phullon, 

leaf).     Leaf-green. 

Chrysalis  (Greek,  chrysews,  golden).     The  pupal  stage  (see  Pupa) 
of  butterflies.     So  called  because  some  chrysalides  are  golden 
yellow  in  colour. 
Cob — The  spike  of  the  Indian  corn  (maize)  plant,  made  up  of  rows  of 

pistillate  flowers  which,  when  ripe,  form  the  corn  grains. 
Combustion  (Latin,  combustum,  a  burn).    The  phenomenon  of  burn- 
ing, in  which  the  majority  of  substances  unite  with  oxygen. 
Cotyledon  (Greek,  kotuledon,  a  cup-like  hollow).     Seed-leaves. 
Cultivation   (Latin,  cultus,  a   tending  or  taking   care  of  a  thing). 
In  agriculture  the  term  denotes  the  operations  of  tillage  where- 
by the  soil  is  brought  into  a  condition  suitable  for  the  economic 
production  of  crops. 

Dicotyledons  (Greek,  dis,  two  ;  kotuledon^  cup-like  hollow).  A  large 
subdivision  of  flowering  plants,  the  members  of  which  have 
embryos  with  two  seed-leaves.  For  other  characters  see  text. 
Dormant  (Latin,  dormio,  I  sleep).  Used  to  denote  the  resting 
condition  of  parts  of  plants — for  instance,  seeds  when  kept  dry, 
tubers  before  starting  into  growth,  etc. 

Effervesce  (Latin,  effervesco,  I  foam  up).     Applied  to  a  bubbling 
action  like  that  which  takes  place  when  an  acid  and  a  carbonate 
come  in  contact. 
Embryo  (Greek,  embnton}.     Used  botanically  for  the  young  plant 

present  in  a  seed. 
Fertility  (Latin,  fertilitas,  fruitfulness).     Used   generally  of  soils. 

"  Fertile  "  is  usually  applied  to  flowers. 

Fertilisation  ( Latin,  fertilisatio^  the  making  fruitful).  The  process 
by  which  the  contents  of  the  pollen  grain  act  on  the  ovules. 
After  fertilisation  the  ovules  develop  into  seeds. 


GLOSSARY  181 

Flower  (Latin,  flos,  a  flower  or  blossom).  The  reproductive  organs, 
i.e.  the  stamens  and  pistil  of  a  plant,  usually  together  with  one 
or  more  protective  coverings.  The  simplest  flowers  consist  of 
stamens  and  pistil  only. 

Fruit  ( Latin,  fructus,  profit  or  produce,  especially  of  land  or  trees). 
The  ripened  ovary  together  with  its  seeds.  Many  things 
commonly  called  vegetables  are  botanically  fruits  ;  for  example, 
tomatoes,  cucumbers,  etc. 

Germination  (Latin,  germinatio,  a  sprouting  forth,  a  budding). 
The  first  stage  of  active  growth  of  a  seed. 

Host — The  plant  which  supplies  "board  and  lodging"  to  a  parasite. 

Humus  (Latin,  humus,  earth,  soil).  Leaf  mould.  The  substance 
formed  by  the  decay  of  vegetable  matter. 

Internode  (Latin,  inter,  between  ;  nodus,  a  knot  or  joint).  The 
portion  of  a  stem  between  two  joints. 

Larva  (Latin,  larva,  a  mask).  The  first  stage  of  active  life  of  an 
insect.  Insects  in  this  stage  are  variously  known  as  maggots, 
caterpillars  or  grubs.  The  name  was  originally  given  because 
the  caterpillar  was  thought  to  hide  or  mask  the  future  butterfly. 

Leguminosae.  The  Latin  word  legumen  was  originally  applied  to 
pulse.  Hence,  the  pod  which  contained  the  peas  from  which 
the  pulse  was  made,  was  called  a  legume,  and  the  name  Legu- 
minosce  given  to  all  the  plants  which  belong  to  the  pod-bearing 
order.  In  addition  to  the  flower,  the  plants  in  this  order  are 
characterised  generally  by  divided  leaves  and  root  nodules. 
It  is  the  second  largest  order  of  flowering  plants,  and  contains 
some  7000  species. 

Manure  (French,  manceuvre,  to  till  by  hand).  The  word  thus 
originally  meant  cultivation  of  the  soil  by  hand.  It  is  now 
restricted  to  the  special  substances  added  to  supply  plant 
food. 

Mechanical  (from  the  Latin,  machina,  a  machine,  a  work  artifically 
made).  The  mechanical  analysis  of  soil  denotes  the  separa- 
tion of  the  constituents  of  the  soil  by  some  method  which  does 
not  entail  any  change  in  composition  of  the  constituents,  e.g. 
by  washing. 

Medullary  rays  (Latin,  medulla,  the  pith  in  plants,  the  marrow  in 
bones).  The  bands  of  tissue  which  pass  from  the  pith,  through 
the  wood,  into  the  inner  bark.  The  "  grain "  in  oak  wood  is 
due  to  the  medullary  rays. 

Monocotyledon  (Greek,  monos,  one  ;  kotuledon,  cup-like  hollow). 
One  seed-leaf.  The  name  given  to  a  division  of  flowering 


182  GLOSSARY 

plants,  the  members  of  which  have  embryos  with  only  one  seed- 
leaf. 
Nitrification  (Latin,  nitrum,  nitre  ;  facto,  I  make).     Applied  to  the 

bacteriological  process  in  the  soil  by  which  various  organic 

substances   containing   nitrogen   are   changed    into    nitrates. 

The  bacteria  bringing  about  the  change  are  called  nitrifying 

bacteria. 
Node  (Latin,  nodus,  a  knot  or  joint).     The  joints  on  a  stem,  at 

which  the  leaves  are  generally  attached. 
Nodules  (Latin,  nodulus,  a  little  knot).     Small,  rounded  swellings  ; 

for  instance,  those  on  the  roots  of  leguminous  plants. 
Nut  (Latin,  nux^  a  nut,  a  fruit  with  a  hard  shell).     Usually  applied 

to  hard  fruits,  which  do  not  split  open,  and  contain  only  one 

seed. 
Organic  (Greek,  organon,  an  instrument  or  implement).    Belonging 

to  life.     The  name  given  to  all  substances  which,  although  not 

alive  themselves,  are  the  results  of  living  processes.     For  in- 
stance, wood,  starch,  hair,  bones,  etc. 
Organism — Any  living  thing,  whether  animal  or  plant. 
Ovary  (Latin,  ovum,  an  egg).     That  portion  of  the  pistil  of  a  plant 

which  contains  the  ovules. 

Ovule  (Latin,  ovulum,  a  little  egg).     The  young  seeds. 
Parasite  (Latin,  parasitus,  a  fellow-boarder,  a  guest).    An  organism 

which  lives  on  and  obtains  its  nourishment  from  another — the 

host.     Distinguished  from  epiphytes  which  live  on  but  do  not 

obtain  nourishment  from  another  organism. 
Petal  (Greek,  petalon,  a  flower  leaf).     One   of  the  leafy  bodies, 

commonly  brightly  coloured,  which  usually  form  the  showy 

portion  of  a  flower. 
Pistil  (L2&\T\,pistillum,  a  pestle).   The  ovary  and  stigma  (which  may 

or  may  not  be  stalked)  of  a  flower.     In  some  plants  the  pistil  is 

pestle-shaped,  hence  the  term  pistil. 
Plastic  (Greek,  plastos,  moulded).     Capable  of  being  moulded  or 

worked   into   various  shapes.      For  instance,  potters'  clay  is 

plastic. 
Plumule  (Latin,  plumula,  a  little  feather).     The  name  given  to  the 

undeveloped  shoot  (that  is,  the  stem  bud)  of  the  embryo.     Its 

appearance  in  such  seeds  as  the  bean  probably  suggested  the 

name. 
Pod — A  dry  (not  fleshy)  fruit,  containing  several  seeds.     A  pod 

usually  splits  open  when  ripe  along  both  sides. 
Pollen  (Latin,  pollen^  anything  as  fine  as  dust  j  hence,  very  fine 


GLOSSARY  183 

flour).      The   powdery  substance  contained  in  the  stamens, 

essential  to  the  fertilisation  of  flowers. 
Pollination— The  act  of  placing  pollen  on  the  stigma  of  a  flower, 

usually,  but   not  necessarily,  followed  by  the   fertilisation  of 

the    flower.      Insects  can  pollinate   flowers,  but  they  cannot 

fertilise  them. 
Propagate  (Latin,  propago,  I  propagate,  I  extend).    To  increase 

the  numbers  of  a  plant  by  means  of  cuttings,  reproduction 

by  seeds,  or  other  methods. 
Pungent  (Latin,  pungo,  I  sting).     Used  to  describe  the  smell  of 

such  a  substance  as  ammonia. 
Pupa  (Latin,  pupa,  a  baby).     The  third  stage  in  the  life  of  many 

insects,   usually   inactive.      The    name   was  given   from   the 

resemblance  of  many  pupae  to  a  baby  bound  up  in  clothes  as  is 

the  custom  in  Southern  Europe.     Pupa  and  chrysalis  refer  to 

the  same  condition. 
Radicle  (Latin,  radix,  a  root ;  hence  radicle,  a  little  root).     The 

young  root  of  the  embryo. 
Respiration  (Latin,  respiratio,  the  act  of  drawing  breath).       Used 

to  denote  the  breathing  process  in  both  plants  and  animals. 
Rudimentary  (Latin,  rudimentum,  a  first  attempt,  a  beginning). 

Often  used    to  describe    parts    of   plants   which    have    not 

reached  their  full  development. 
Scutellum  (Latin,  scutulum,  a  little  shield).     A  descriptive  name  for 

the  body  on  the  embryo  of  a  grass,  by  means  of  which  it 

dissolves  and  absorbs  the  food-reserve  stored  up  in  the  seed. 
Sections  (Latin,  sectio,  a  cutting).     Thin  slices  cut  from  a  plant. 

They  may  either  be  cut  across  the  stem — cross-sections  ;  or  cut 

lengthwise — longitudinal  sections. 
Segments    (Latin,   segmentum,   a    division   or    a   portion).      The 

divisions,  or  rings,  which  make  up  the  body  of  an  insect. 
Sepal  (from  Greek,  skepas,  covering  or  shelter).     One  of  the  leafy 

bodies,  commonly  green,  which  form  the  outermost  portion  of 

the  flower,  and  usually  make  a   protective  wrapping  to  the 

more  delicate  inner  portions. 
Species  (Latin,  species,  a  kind  or  sort).     All  those  animals  or  plants 

are  said  to  be  of  the  same  species  which  do  not  vary  more 

from  one  another  than  might  be  expected  in  the  produce  of 

the  same  parents. 
Stamen  (Latin,  stamen,  a  thread).     One  of  the  essential  parts  of  a 

flower,   consisting  usually  of  a  stalk,  bearing  a  pollen-bo* 

containing  the  pollen  grains. 


184  GLOSSARY 

Stigma  (Greek,  stigma,  a  spot).  The  portion  of  the  pistil  which 
receives  the  pollen.  It  is  often  hairy  or  sticky. 

Stipules  (Latin,  stipula,  straw,  stubble).  The  bodies  borne  where 
a  leaf  joins  on  to  a  stem  ;  not  present  in  all  plants. 

Stoma — (plural,  stomata) — (Greek,  stoma,  a  mouth).  The  small 
pores  in  the  surfaces  of  leaves,  and  other  green  parts  of  plants. 

Sucker.  This  is  used  botanically  in  two  senses,  (i)  For  a  branch 
which  starts  underground,  and  then  comes  above.  (2)  For  a 
special  sucking  apparatus  by  means  of  which  some  young 
plants  empty  their  seeds  of  food. 

Tendril — A  thin  structure,  branched  or  not,  by  means  of  which  a 
plant  climbs.  Stems  and  leaves  are  frequently  modified  to 
form  tendrils. 

Transpiration  (Latin,  trans,  across  ;  spiro,  I  breathe).  The  giving 
off  of  water- vapour  through  the  stomata  of  plants. 

Tuber  (Latin,  tuber,  a  swelling).  A  thickened,  usually  underground 
structure,  which  may  be  a  root  or  stem.  Important  as  store- 
houses of  plant  food. 

Variation  (Latin,  variatio,  a  difference).  Used  to  express  the 
tendency  of  living  things  to  differ  to  some  extent  from 
the  ordinary  type.  The  differences  which  enable  us  to  dis- 
tinguish different  persons  from  one  another,  afford  an  everyday 
illustration  of  variation  in  human  beings. 

Vitality  (Latin,  mtalis,  of  or  belonging  to  life).  Seeds,  for  instance, 
are  said  to  retain  their  vitality  so  long  as  they  are  capable  of 
growing  when  placed  under  suitable  conditions. 


APPENDIX  I 

SUGGESTED  COURSES 

IN  schools  taking  up  this  work  in  autumn,  the  following  course  is 

suggested  : — 

Chap,  i . — Parts  of  a  seed. 

Plant  food  in  seeds. 

Conditions  of  germination. 
Chap.  2. — The  general  characters  of  roots. 
Chap.  3. — The  general  characters  of  stems. 

The  life-history  of  a  crocus  or  gladiolus. 

The  structure  of  stems. 
Chap.  4. — Winter  buds. 

The  structure  of  leaves. 
Chap.  5. — Mechanical  analysis  of  soil. 

Water  in  soils. 

Effect  of  frost  on  rocks. 

Vegetable  matter  in  soils. 

Chalk  in  soils. 

The  ground  in  the  school  garden  should  be  dug  up,  and  if 
possible  the  beds  and  paths  laid  out  before  the  frosts  set  in. 

In  the  spring  the  remaining  portions  of  Chap.  I.  can  be  under- 
taken, and  the  order  in  the  book  followed  as  far  as  found  convenient, 
care  being  taken  to  start  the  manurial  experiments,  collection  of 
weeds,  and  observations  on  insect  pests  at  an  early  date. 

When  the  work  is  commenced  in  the  spring,  the  weather  offers 
no  obstacles.  Care  must  be  taken  to  examine  the  opening  of  leaf- 
buds,  the  life-history  of  the  crocus,  and  to  begin  the  experimental 
work  on  seedlings  at  an  early  date. 

If  not  already  done,  the  school  garden  should  be  at  once  put 
into  order,  beds  and  paths  laid  out,  and  seeds  sown  for  transplanting 
into  the  plots  for  manurial  experiments. 

As  in  the  previous  case,  an  early  beginning  should  be  made  in 
recording  observations  on  flowers,  weeds,  insect  pests,  etc. 

185  1*2 


APPENDIX  II 

APPARATUS   AND   MATERIALS   REQUIRED 

6  wide-mouthed,  corked  bottles,  e.g.,  i  Ib.  jam  bottles. 

3  small,  narrow-necked  bottles. 

2  square,  wide-mouthed  bottles,  e.g.,  pickle  bottles,  and  corks  to 

fit. 
12  test-tubes,  about  |  in.  diameter,  and  corks  to  fit. 

1  thistle-funnel. 
6  dinner  plates. 

4  tumblers. 

2  glazed  jam  pots. 

2  beakers  (4  oz.). 

3  glass  funnels  (3  in.  diameter). 

i  glass  tube  (i  ft.  long,  f  in.  diameter). 

6  glass  plates  (4x3  in.),  e.g.)  clean  quarter-plate  negative  glasses. 

1  straight  lamp-chimney. 

4  saucers. 

2  doz.  flower-pots  (5  in.). 
64  flower-pots  (8  in.). 


£  Ib.  starch. 

|  Ib.  paraffin  wax. 

2  oz.  iodine  solution. 

1  qt.  methylated  spirit. 
4  oz.  vaseline. 

\  Ib.  soda  lime. 

\  Ib.  caustic  potash. 

\  Ib.  paraffin  wax. 

2  oz.  Fehling's  solution. 

186 


APPENDIX  II  187 

Ib.  chalk.  ^ 

Ib.  sulphate  ammonia.       Lar^er    quant'"es    lf    mammal 

Ib.  basic  slag.  experiments  are  to  be  carried 

Ib.  sulphate  potash.       J         out  in  scho°l  Sarden' 

oz.  calcium  nitrate. 

oz.  potassium  nitrate. 

oz.  magnesium  nitrate. 

oz.  potassium  phosphate. 

oz.  iron  chloride. 
Nitrate  of  soda. 
Dried  blood. 

Phosphate  of  lime,     f  A  small  quantity  of  each  as  a  specimen. 
Basic  slag. 
Kainit. 
Soap. 

Kerosene  oil. 
Whale-oil  soap. 
Cardboard. 
Tinfoil. 
Copper  wire. 
Camels'  hair  brushes. 

1  Ib.  shot. 
Muslin. 

2  doz.  sugar  bags. 

Fine  wire-gauze  (i  sq.  foot). 

Sealing-wax. 

Beeswax. 

Resin. 

Coco-nut  fibre  refuse. 

Indian  ink. 

Budding-knife. 

Grafting-knife. 

Budding-tape  (see  instructions  in  Chap.  III.) 

i  pr.  fine  forceps. 

i  pr.  sharp-pointed  scissors. 

£  ream  botanical  drying-paper  (16  x  12). 

£  ream  botanical  mounting-paper  (16  x  ioi). 

i  pr.  boards  (17  x  13). 

Gummed  labels. 

6  pieces  of  flannel  (each  size  dinner  plate). 

Balance  and  weights,  to  weigh  from  100  to  ^  gramme. 


188  APPENDIX  II 

Ordinary  scales  and  weights  to  weigh  to  5  Ib. 

Box  with  removable  glass  or  wooden  front. 

Box  with  one  side  removable  and  slot  in  bottom. 

2  stakes  and  lines. 

Levelling-tool. 

Ordinary  sieves,  i",  £",  J"  mesh. 

Brass  sieves,  2,  I,  J  mm.  mesh. 

6  stout  wooden  seed-boxes,  4  to  6  ins.  deep. 

4  stout  wooden  boxes,  2'  x  2'  x  i'. 

Box  for  rearing  insects  in. 

Triplet  pocket  lens. 


INDEX 


Acorns,  8,  16 

Albumen,  5 

Alder,  147,  154 

Anemone,  154 

Apple,  83,  91,  151,  162;  root 
system,  31  ;  stipules,  67 

Apricot,  4 

Artichoke,  45 

Ash,  21,  46,  56,  81 

Assimilation,  77-80 

Atmosphere  and  plants,  77  ;  com- 
position of,  76 

Avens,  162 


B 


Bacteria  in  soils,  123 

Balsams,  53,  152,  157 

Bark,  46 

Barley,  4,  5,  21,  23,  147,  155;  root 

system,  31 

Basic  phosphate,  131  ;  slag,  131 
Bean,  4,  13,  23,  53,  147,  154 
Beech,   78,    165  ;    root  system,  31  ; 

stipules,  67 
Beet,  5,  23,  27,  69,  91  ;  arrangement 

of  leaves,  75 
Beetle,  life-history,  171 
Begonia,  propagation  of,  29,  40 
Pind-weed,  56 
189 


Birch,  162 

Blackberry,  70,  162 

Blood,  as  manure,  130 

Bluebell,  150 

Box,  74,  165 

Breathing  of  plants,  78 

Broad  bean,  21 

Broom,  81,  86,  165 

Bryony     (black),     leaf-veins,     71  ; 

(white),  tendrils,  45,  $6 
Buckwheat,  4,  5,  21  ;  germination,  9 
Budding,  48,  57,  62 
Bulbs,  69 
Burdock,  162 
Butter-burr,  150 
Buttercup,  154 
Butterfly,  life-history,  170 


Cabbage,  4,  23  ;  leaf-buds,  67,  81 

Cambium,  46,  48 

Canterbury  bell,  141 

Carbon,  76,  91  ;  dioxide,  76,  91 

Carrot,  5,  23,  27,  56,  143 

Cassava,  28 

Castor-oil  plant,  n,  21 

Caterpillar,  life-history,  169 

Celandine,  166 

Cereals,  II,  147 

Chalk,  91  ;  in  soils,  no,  120 

Chili  saltpetre,  130 


190 


INDEX 


Chlorophyll,  77 

Chrysalis,  170 

Chrysanthemums,  28 

Clay,  103,  105 

Cleavers,  150,  161 

Climbing  organs,  70 

Clover,  23,  29,  82  ;  stipules,  67 

Coleus,  37,  38,  78,  157 

Coltsfoot,  165 

Compost  heaps,  109 

Copper  beech,  78 

Corn,  46 

Corn  spurrey,  166 

Cotyledons,  3,  7 

Couch  grass,  53,  165 

Creeping  jenny,  43,  45,  54 

Crocus,  45,  46,  55,  67,  69,  83 

Cross-fertilisation,  146,  156 

Crow-foot,  140 

Cucumber,    4,    21,    23,    154,    156; 

fertilisation,     144 ;     germination, 

8  ;  tendrils,  56 
Currant,  151,  162 
Cuscuta,  29 
Cuttings,  propagation  by,  37 


Elm,  31,  46,  47,  56 
Embryo,  4 

Enchanter's  nightshade,  162 
Evening  primrose,  153 
Explosive  fruits,  152 


F 


Felspar,  102,  105 

Fertilisation  of  flowers,  143 

Flag,  44 

Flax,  7,  29 

Flies,  life-history,  173 

Flower,  parts  of,  139,  154 

FooJ  of  plants,  78,  93,  132 

Foxglove,  150 

French  bean,  3,  8 

Frog's-bit,  roots,  25  ;    root-cap,  31, 

74 
Fruits,     148  ;     dispersal    of,    149  ; 

explosive,  152 
Furze,   152,   162,   165  ;    leaves,   67, 

74,  81,  86 
Fuchsia,  93,  98 


Daisy,  156 

Damson,  151 

Dandelion,  75,  91,  159,  165 

Date  palm,  21 

Dead-nettle,  $3.  85»  *54 

Dicotyledons,    root     systems,     31  ; 

seeds,  5  ;  stems,  47 
Dock,  67,  8 1 
Dodder,  29 
Duck-weed,  leaves,    74 ;   root-caps, 

31 

E 

Earth-worms,  work  of,  107 
Elderberry,  i$i 


Garden  pea,  leaf-stalk,  70 

Geranium,  37,  82,  96,  154,  155 

Germination,  6  ;  conditions  of,  1 3 

Gladiolus,  55,  83 

Goat's-beard,  160 

Gooseberry,  39 

Goose-grass,  161 

Grafting,  48 

Grapevine,  45,  151,  162;  tendrils, 

56 

Grasses,  73,  147  ;  stem  structure,  57 
Gravel,  103 
Gravitation,  35 
"Green  dressing,"  126,  129 
Green  fly,  172 


INDEX 


191 


Ground  ivy,  adventitious  roots,  27, 

43 

Groundsel,  85,  156 
Grub,  171 
Guano,  129 
Guelder  rose,  165 


II 


Harebell,  141 

Haricot  bean,  21 

Hawthorn,  46,  56  ;  stipules,  66 

Hazel-nut,  54,  147,  154 

Heart-wood,  47 

Heather,  67,  81,  86,  165 

Hemp- agrimony,  162 

Hollyhock,  155 

Honeysuckle,  66,  81 

Hop,  56 

Horse  chestnut,  16,  21,  46,  54,  56, 

66  ;  buds,  68,  81,  82 
Host  plants,  29 

House-leek,  41,  53,  67,  74,  81,  86 
Humus,  107 

Hyacinth,  150  ;   bulb,  84,  91,  161 
Hydrocharis,  25,  31,  74 


I 


Insects  and  flowers,  144 
Internode,  42 

Iris,  44,  45,  54,  67,  69,  71,  83,  85 
Ivy,  adventitious  roots,  28,  54 


J 


Jerusalem  artichoke,  44,  54 


K 

Kainit,  131 
Kidney  bean,  3,  7 
Killing-bottle,  177 


Laburnum,  47 

Laurel,  74 

Leaf,  66 ;    arrangement,  75 ;    as  a 

climbing  organ,   70  ;   blade,   81  ; 

green,  77  ;  pores,  73  ;  stalk,  66,  81  ; 

structure,  70,  84  ;  uses  of,  67,  8 1  ; 

veins,  71,  85 
Leguminous    plants,     nodules     on 

roots,  137 

Lemna,  leaves,  74  ;  root-cap,  31 
Lettuce,  23,  91,  160;  leaf-bud,  67, 

81 

Lilac,  8 1,  85 

Lily,  parts  of  flower,  140,  154 
Lime  tree,  147  ;  green  fly  on,  172 
Lime,  as  manure,  106 
Lime-water,  91 
Linseed,  7 


M 


Maggot,  173 

Maize,  5,  21,  155  ;  root  system   31  ; 

structure  of  stem,  48,  57 
Manures,    128  ;    experiments   with, 

134 

Maple,  54,  70,  81 
Marigold,  21,  53 
Marrow,  21,  154,  156 
Marvel  of  Peru,  4 
Medullary  rays,  48 
Michaelmas  daisy,  156 
Mistletoe,  29  ;  seed  dispersal,  1 52 
Molluscs,  183 

Monocotyledons,  seeds,  5  ;  stems,  48 
Moth,  170 
Mullein,  74 
Mustard,  23 

N 

Nasturtium,  66,  70 
Nitrate  of  soda,  130 


192 


INDEX 


Nitrates,  123 
Nitrogen,  76,  80,  81 
Nodules,  137 


Oak,  47,  76,  81,  91 

Old  man's  beard,  70 

Onion,  10,  21,  23,  69 

Orange,  4 

Orchids,  pollination  of,  146 

Ovary,  140 

Ovules,  140,  142,  148 

Oxalis,  163 

Oxygen,  76 


Palms,  germination,    10 ;    structure 

of  stem,  57 
Pandanus,  roots,  25 
Pansy,  stipules,  82 
Parsley,  23 
Parsnip,  23 

Pea,  4,  8,  13,  21,  23,  153 
Peach,  151 
Pear,  stipules,  67 
Pests  of  plants,  1 74  ;  remedies  for, 

177 

Petals,  140,  142  ;  uses  of,  144 
Phosphate  of  lime,  130 
Pilewort,  166 
Pine,  74,  H7,  ^54,  160 
Pistil,  142  ;  uses  of,  144 
Pith,  48 

Plant  food,  78,  93,  132 
Plum,  fruit,  151,  162 
Plumule,  3,  6 
Pollen,  140,  142,  144 
Poppy,  150;  fruit,  161 
Potato,  55,  79,  83 
Primrose,  53,  141,  154 
Privet,  53  ;  leaf-buds,  67,  81 
Pupa,  170 
Pyrethrum,  I  $6 


Radish,  4,  21,  69 

Radicle,  3,  6 

Raspberry,  151,  162 

Respiration  of  plants,  78 

Rhizomes,  44 

Rock  rose,  165 

Root,  24  ;  cap,  23,  30  ;  hairs,  24, 
30  ;  systems,  30 

Roots,  absorption  by,  34 ;  adventi- 
tious, 27,  28,  38,  43,  54;  and 
gravitation,  35 ;  and  water,  37 ; 
growth  in  length,  32  ;  growth  in 
thickness,  31  ;  of  seedlings,  24  ; 
uses  of,  26 

Roses,  37,  56,  147,  154,  155,  172  ; 
propagation  of,  28,  39 


Salad,  burnet,  165 

Salsify,  1 60 

Sand,  103 

Sap,  80 

Sapwood,  47 

Scale  leaves,  44 

Scarlet  runner,  8,  21,  56 

Scion,  49 

Screw-pine,  roots,  25  ;  root-caps,  30 

Sea-kale,  81 

Sea-purslane,  81,  86 

Sea-rocket,  81,  86 

Sedge,  161 

Seed  beds,  16,  17 

Seed-coat,  3,  7 

Seed-leaves,  3,  8 

Seed,  parts  of,  2 

Seeds,  I,  6,  140;  albuminous,  5;  dis- 
persal of,  158  ;  exalbuminous,  5  ; 
germination  of,  6,  13 ;  testing 
vitality  of,  22 

Seedlings,  raising,  15  ;  variations 
in,  153 

Sepals,  142  ;  uses  of,  144 


INDEX 


193 


Shellfish,  173 

Shoot,  41 

Silt,  103 

Skeleton  leaves,  85 

Slug,  173 

Snail,  173 

Soil,  101,  106,  no;  mechanical 
analysis  of,  112;  preparation  of, 
for  sowing  seeds,  15  ;  vegetable 
matter  in,  118  ;  water  in,  114 

Solomon's  seal,  44,  45 

Sow-thistle,  81 

Specimens,  preserving,  166 

Stamens,  140,  142  ;  uses  of,  144 

Starch,  78,  97 

Stems,  41  ;  increase  in  thickness  of, 
46  ;  structure  of,  46,  56  ;  uses  of 
42,  54  ;  as  storehouses,  43  ;  as 
climbing  organs,  45  ;  of  dicoty- 
ledons, 46 ;  of  monocotyledons, 
48 

Stigma,  142 

Stipules,  66,  82 

Stock,  49 

Stomata,  71,  73 

Strawberry,  45,  151,  162 

Style,  142 

Sugar-cane,  propagation  of,  28 

Sulphate  of  potash,  131 

Sunflower,  75,  155 

Superphosphate,  131 

Sweet  pea,  2 1,  70,  84,  157 

Sycamore,  21,  83 


Tomato,  21,  23,  157 

Transpiration,  73,  85 

Traveller's-joy,  70,  84 

Tubers,  44 

Tulip,  parts  of  flower,  140,  154 

Turnip,  27,  69 

Twitch,  165 


Vanilla,  pollination  of,  146 
Veins  of  leaves,  70,  85 
Vetch,  21,  81,  84,  163 
Violet,  75,  91,  152 
Vitality  of  seeds,  22 
Vegetable  marrow,  1 56 


W 


Wallflower,  154 
Water  in  soils,  104,  114 
Water-lily,  161  ;  leaves,  74 
Watercress,  adventitious  roots,  28, 

38 

Weeds,  164 
Wheat,  4,    5,    13,   21,   23;    flower, 

155  ;  root  system,  31 
Whortleberry,  165 
Willow,  37,  147,  154 
Willow-herb,  160 
Wind-pollinated  flowers,  147 
Wood,  46 

Wood-sanicle,  150,  162 
Wounds,  healing  of,  64 


Tapioca,  28 
Thistle,  160 
Tiger  lily,  169 


Yew,  165 


Printed    by 

Oliver   and   Boyd 

Edinburgh 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  5O  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


LD21-100m-7,'33 


180730 


